Foot to Inch Converter
Convert feet to inches with our free online length converter.
Quick Answer
1 Foot = 12 inches
Formula: Foot × conversion factor = Inch
Use the calculator below for instant, accurate conversions.
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Foot to Inch Calculator
How to Use the Foot to Inch Calculator:
- Enter the value you want to convert in the 'From' field (Foot).
- The converted value in Inch will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Length category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Foot to Inch: Step-by-Step Guide
Converting Foot to Inch involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Foot = 12 inchesExample Calculation:
Convert 10 feet: 10 × 12 = 120 inches
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Need to convert to other length units?
View all Length conversions →What is a Foot and a Inch?
The foot is a unit of length in the British imperial and United States customary systems of measurement. Since the international yard and pound agreement of 1959, one foot has been defined as exactly 0.3048 meters, which equals precisely 12 inches or 1/3 of a yard.
The foot is denoted by the symbol ft or by a single prime mark ′ (e.g., 6′ means 6 feet). When combined with inches, the notation uses both symbols: 5′-9″ means 5 feet, 9 inches (69 inches total, or approximately 1.75 meters).
The foot occupies a unique position in the imperial system as the most commonly used length unit for human-scale measurements—distances that relate directly to human body size, living spaces, and immediate environments. While inches handle smaller precision work and miles cover long distances, feet describe the comfortable middle ground of everyday human experience.
The inch is a unit of length in the British imperial and United States customary systems of measurement. Since the international yard and pound agreement of 1959, one inch has been defined as exactly 2.54 centimeters. This makes the inch equal to 1/12 of a foot, 1/36 of a yard, and 25.4 millimeters precisely.
The inch is denoted by the symbol in or by a double prime mark ″ (e.g., 5″ means 5 inches). In engineering drawings and construction blueprints, dimensions are typically expressed in feet and inches (e.g., 5′-3″ means 5 feet, 3 inches).
Unlike the metric system with its consistent decimal relationships, the inch exists within a complex system where 12 inches make a foot, 3 feet make a yard, and 1,760 yards make a mile. This fractional system reflects the inch's origins in human-scale measurements rather than mathematical convenience.
Note: The Foot is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Inch belongs to the imperial/US customary system.
History of the Foot and Inch
The foot represents one of humanity's oldest measurement units, with origins predating written records.
Ancient Origins: The foot concept emerged independently in multiple ancient civilizations, all based on the approximate length of a human foot. The Egyptian royal cubit (20.6 inches) divided into smaller units approximating foot measurements. The Greek pous measured roughly 11.6 inches, while the Roman pes (foot) standardized at approximately 11.65 modern inches (296 mm).
Roman Influence: When Romans conquered Britain, they brought the pes, which heavily influenced British measurement traditions. The Roman foot divided into 12 unciae (inches), establishing the 12-inch relationship that persists today. Even after the Roman Empire fell, this measurement structure survived in English-speaking regions.
Medieval Variations: Throughout medieval Europe, foot measurements varied dramatically by region and ruler. Different "feet" existed simultaneously—the Tower foot, the London foot, and various guild-specific feet. King Henry I of England (r. 1100-1135) reportedly standardized the yard as the distance from his nose to his outstretched thumb, making the foot one-third of that distance.
Statute Definitions: In 1266, King Henry III's Composition of Yards and Perches defined relationships between feet, yards, and rods for land measurement. The 1324 statute by Edward II attempted further standardization, though regional variations persisted for centuries.
English Standardization: The British Weights and Measures Act of 1824 established the Imperial foot throughout the British Empire. This Imperial foot differed slightly from the US foot after American independence—the US maintained measurements from pre-1824 British standards.
1959 International Agreement: The international yard and pound agreement unified English-speaking countries. The United States, United Kingdom, Canada, Australia, New Zealand, and South Africa agreed that 1 yard equals exactly 0.9144 meters, making 1 foot exactly 0.3048 meters (304.8 mm). This ended over a century of slight differences between US and British feet.
US Survey Foot Retirement: From 1893 to 2023, the United States maintained two different feet—the international foot (0.3048 m exactly) and the US survey foot (0.30480061 m, or 1200/3937 meters). The survey foot was used for land surveys and mapping. On January 1, 2023, the National Geodetic Survey officially retired the US survey foot, making all American measurements use the international foot exclusively.
Aviation Standard: In 1947, the International Civil Aviation Organization (ICAO) standardized altitude measurements worldwide in feet. This remains universal today—even pilots in fully metric countries like France, Germany, and Japan report altitude in feet. This standardization prevents confusion and enhances safety in international aviation.
The inch has one of the longest continuous histories of any modern measurement unit, with roots stretching back over two millennia.
Ancient Origins: The Roman "uncia" (meaning one-twelfth) represented 1/12 of a Roman foot, similar to our modern inch. When the Romans occupied Britain, they brought this measurement system with them, establishing a tradition that would last far beyond their empire.
Medieval Definitions: Throughout the Middle Ages, various rulers attempted to standardize the inch using body-based measurements. King Edward I of England ordered in 1305 that an inch should equal the length of three barleycorns (grains of barley) laid end to end. King Edward II formalized this in 1324, making it English law. Other definitions included the width of a man's thumb at the base of the nail.
Regional Variations: Before standardization, different regions maintained slightly different inch measurements. The Tower inch, Merchant's inch, and Cloth inch all differed slightly, causing confusion in trade and construction. The French pouce (thumb) was approximately 1.066 English inches.
1959 International Agreement: The modern inch was defined by the international yard and pound agreement signed by the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. They agreed that 1 yard equals exactly 0.9144 meters, making 1 inch exactly 2.54 centimeters. This ended centuries of slight variations and created perfect mathematical alignment between imperial and metric systems.
US Survey Inch: For a time, the US maintained two slightly different inches—the international inch (2.54 cm exactly) and the US survey inch (2.540005080010160020 cm, based on the Mendenhall Order of 1893). As of January 1, 2023, the US officially retired the survey inch, making all American measurements use the international inch exclusively.
Common Uses and Applications: feet vs inches
Explore the typical applications for both Foot (imperial/US) and Inch (imperial/US) to understand their common contexts.
Common Uses for feet
Residential Construction and Remodeling
Home construction in America operates in feet for layout and square feet for area calculations. Foundation plans show exterior dimensions (e.g., 40' × 60' house footprint = 2,400 sq ft per floor). Interior walls use standard 8-foot studs for 8-foot ceiling heights, or 9-foot and 10-foot studs for taller ceilings.
Lumber lengths come in 2-foot increments: 6', 8', 10', 12', 14', 16' boards. This modular system allows efficient layout with minimal waste. A wall spanning 16 feet can use a single 16-foot top plate rather than joining shorter pieces.
Plywood and drywall sheets measure 4' × 8' (32 square feet per sheet). With standard 16-inch stud spacing, three studs span 48 inches (4 feet), perfectly matching sheet width. This dimensional coordination throughout the building industry stems from foot-based planning.
Standard door heights are 6'8" (80 inches), accommodating people up to about 6'5" with clearance. Door widths vary: 2'6" (30"), 2'8" (32"), 3'0" (36"). Window rough openings are specified in feet and inches: 3'0" × 4'0" window.
Architectural Design and Floor Plans
Architects draw floor plans at scales based on feet: 1/4" = 1'0" (common residential) or 1/8" = 1'0" (larger buildings). Blueprint dimensions appear as feet-inches notation: 12'-6" means 12 feet, 6 inches (150 inches total).
Room planning uses standard furniture dimensions understood in feet:
- Queen bed: approximately 5' × 6'8"
- King bed: approximately 6'4" × 6'8"
- Sofa: 6-8 feet long
- Dining table (seats 6): 3' × 6'
- Dining table (seats 8): 3'6" × 7'
Designers ensure adequate circulation space: 3 feet minimum for walkways, 4 feet preferred. A 12' × 15' bedroom comfortably fits a king bed with nightstands and leaves walkway space.
Building codes specify requirements in feet: egress windows must have 5.7 square feet of opening, stair landings must be at least 3 feet deep, hallways must be at least 3 feet wide.
Commercial Real Estate and Office Space
Commercial property leasing operates in square feet. Office space leases quote price per square foot annually: $30/sq ft/year means a 1,000 sq ft office costs $30,000 per year ($2,500/month). Retail space commands higher rates, often $40-100+/sq ft/year in prime locations.
Office planning uses square feet per employee: 150-250 sq ft per person including shared spaces, or 50-75 sq ft for individual workstations. A company with 50 employees needs approximately 7,500-12,500 square feet total.
Commercial buildings describe floor plate size in square feet: a 100' × 120' floor plate provides 12,000 sq ft of rentable space per floor. Column spacing (typically 20-30 feet in modern buildings) affects layout flexibility.
Retail space measures street frontage in feet—20 feet, 40 feet, 60 feet of storefront directly influences visibility and foot traffic. Corner locations with frontage on two streets command premium rent.
Swimming and Aquatics
Swimming pools use feet for all dimensions. A typical residential pool might measure 16' × 32' (512 sq ft surface area) with shallow end 3'6" and deep end 8'0". Lap pools are typically 8-10 feet wide by 40-50 feet long.
Competition pools follow precise foot-based specifications:
- Short course: 75 feet (25 yards, 6-8 lanes)
- Olympic pool: 164 feet (50 meters, 10 lanes) with 6'6" minimum depth
Pool safety regulations require depth markers at 3', 4', 5', 6', 8', and deeper. "NO DIVING" signs appear in areas less than 9 feet deep. These measurements help swimmers quickly assess safety.
Interior Design and Space Planning
Interior designers work in feet for furniture placement and room flow. Industry standards include:
- Seating area: 8' × 10' minimum for sofa, chairs, coffee table
- Dining area: Allow 3 feet per chair, 3-4 feet circulation around table
- Kitchen work triangle: 12-26 feet total (sum of distances between sink, stove, refrigerator)
- Island clearance: 3-4 feet on all sides for traffic flow
- TV viewing distance: 1.5-2.5× the diagonal screen size
A 12' × 18' living room (216 sq ft) allows space for a seating arrangement, TV console, and traffic flow. A 10' × 10' room (100 sq ft) feels cramped with more than a bed and dresser.
Window treatment specialists measure window width and height in feet and inches to calculate fabric requirements. Curtains typically extend 4-8 inches beyond window frame on each side, requiring precise foot-inch measurements.
Theater and Entertainment Venues
Stage dimensions, screen sizes, and venue layouts use feet:
- Proscenium width: 30-50 feet (typical theater)
- Stage depth: 20-40 feet
- Fly space: 60-80+ feet (above stage for scenery)
- Movie screen width: 40-90 feet (commercial theaters)
- IMAX screen: 72' × 52' (standard), 97' × 76' (largest)
Theatrical lighting positions specify trim height (distance from stage floor to light) in feet: 12', 18', 24'. Sound engineers place speakers based on feet of distance to achieve proper coverage—one speaker per 30-50 feet of venue length.
Venue capacity relates to square footage: 6-7 square feet per person for standing room, 10-12 sq ft per person for chair seating with aisles, 15-20 sq ft per person for banquet seating with tables.
Firefighting and Emergency Services
Fire departments specify equipment reach in feet: 75-foot aerial ladders, 100-foot platform trucks. Building codes restrict height based on fire equipment access—many jurisdictions limit wood-frame construction to 75 feet (roughly 7 stories) due to ladder reach limitations.
Hose lengths standardize at 50 feet or 100 feet. Firefighters calculate distance from hydrant to building entrance in feet to determine hose requirements. Water pressure calculations use feet of elevation: each foot of elevation change requires roughly 0.43 PSI pressure adjustment.
Emergency responders use feet for scene measurements: accident scenes, crime scenes, and disaster areas document positions and distances in feet. "Vehicle came to rest 150 feet beyond point of impact" provides clear spatial understanding.
Landscaping and Irrigation
Landscape contractors measure yards in feet for material calculations and cost estimates. Sod comes in rolls typically 2' × 5' (10 sq ft). Mulch, topsoil, and gravel calculate coverage in square feet at various depths: 1 cubic yard covers 324 sq ft at 1 inch depth, or 81 sq ft at 4 inches depth.
Irrigation system design uses feet for sprinkler spacing: 15-foot spacing for spray heads, 30-40 foot spacing for rotary heads. Drip irrigation calculates emitter placement in feet: 12-18 inches for flower beds, 2-3 feet for shrubs.
Tree planting requires spacing in feet based on mature spread: 15-20 feet apart for small trees, 30-40 feet for large shade trees, 50+ feet for massive specimens. "Plant trees 30 feet from building foundations" prevents root damage to structures.
Property grading specifies slope in inches per foot: 2-3 inches of drop per 10 feet of distance away from house foundations prevents water intrusion.
When to Use inches
Home Construction and Renovation
Residential construction in the United States operates almost exclusively in inches and feet. Standard framing uses 16-inch or 24-inch on-center stud spacing, creating modular dimensions that align with 48-inch-wide drywall and plywood sheets. Contractors calculate materials in board feet and square footage, but individual measurements are precise to 1/16 inch.
Kitchen cabinets come in 3-inch width increments (12″, 15″, 18″, 21″, 24″, 27″, 30″, 33″, 36″), with standard depth of 24 inches for base cabinets and 12 inches for wall cabinets. Countertop height standardizes at 36 inches, while bar counters sit at 42 inches. These dimensions have remained unchanged for decades, creating an entire ecosystem of compatible fixtures, appliances, and hardware.
Tile installation relies on precise inch measurements. Floor tiles commonly measure 12″ × 12″, 12″ × 24″, or 24″ × 24″. Wall tiles might be 3″ × 6″ subway tiles or 4″ × 4″ ceramic squares. Grout line spacing typically runs 1/16″ to 1/4″ depending on tile type. Tile setters work to extremely tight tolerances, as even 1/16-inch variation across a room becomes visibly noticeable.
Manufacturing and Machining
American manufacturing maintains imperial measurements for historical and practical reasons. Machine shops operate in decimal inches (0.001″ = 1 "thou" or 1 "mil"), with precision machining achieving tolerances of ±0.0001″ (one ten-thousandth of an inch, called a "tenth").
Thread specifications use threads per inch (TPI): 1/4″-20 means a 1/4-inch diameter bolt with 20 threads per inch. Common thread pitches include coarse (UNC) and fine (UNF) standards, with sizes ranging from #0-80 (tiny electronic screws) to several inches in diameter for industrial equipment.
Sheet metal thickness traditionally uses gauge numbers (inversely related to thickness in inches). 20-gauge steel is approximately 0.036 inches thick, while 10-gauge is 0.135 inches. However, modern manufacturing increasingly specifies thickness in decimal inches (0.063″ aluminum sheet) for clarity.
CNC (Computer Numerical Control) machines can work in either inches or millimeters, but American shops predominantly program in inches. A machinist might bore a hole to 0.5005″ diameter to accept a 1/2-inch precision shaft with 0.0005″ clearance.
Fasteners and Hardware
The American fastener industry operates entirely in imperial measurements. Screw and bolt diameters are specified in fractions (1/4″, 5/16″, 3/8″, 1/2″) or gauge numbers (#4, #6, #8, #10). Thread pitch is given in threads per inch.
Common bolt sizes and their applications:
- 1/4″-20: Electronics, light fixtures, small brackets
- 5/16″-18: Medium structural connections, automotive
- 3/8″-16: Heavy brackets, machinery, automotive chassis
- 1/2″-13: Structural steel, heavy machinery, trailer hitches
- 5/8″-11: Building construction, large structural connections
- 3/4″-10: Industrial equipment, heavy structural steel
Hex keys (Allen wrenches) come in fractional inch sizes: 1/16″, 5/64″, 3/32″, 1/8″, 5/32″, 3/16″, 7/32″, 1/4″, 5/16″, and 3/8″. Metric hex keys are incompatible—a 5mm key is 0.197″, close to but not quite matching 3/16″ (0.1875″) or 1/4″ (0.25″).
Display Technology and Photography
Television and monitor sizes are universally described by screen diagonal in inches, even in metric countries. This convention originated with cathode ray tubes, where the diagonal measurement corresponded to the visible screen area inside the bezel.
Common display sizes and their uses:
- 24″ monitors: Standard office workstation
- 27″ monitors: Popular desktop size, ideal for 1440p resolution
- 32″ monitors: Large desktop or small TV
- 43″ TVs: Small bedroom TV
- 55″ TVs: Most popular living room size
- 65″ TVs: Premium living room standard
- 75″ TVs: Home theater
- 85″+ TVs: Luxury home cinema
Photography inherited imperial measurements from early camera equipment. Sensor sizes reference inches in confusing ways—a "1-inch sensor" is actually much smaller (13.2 × 8.8 mm), referencing the outer diameter of an obsolete video camera tube rather than the actual sensor dimensions.
Large format photography uses inch measurements directly: 4×5″ and 8×10″ sheet film, or medium format 6×4.5cm, 6×6cm, 6×7cm (which are actually metric despite being called 120 film).
Plumbing and Pipe Systems
Plumbing pipe sizes in the US use nominal measurements that don't match actual dimensions. A "1/2-inch pipe" has an inside diameter of approximately 0.622″ and outside diameter of 0.840″. This naming convention dates back to when pipe walls were much thicker.
Common pipe sizes and uses:
- 1/2″ nominal: Standard water supply lines to fixtures
- 3/4″ nominal: Main water supply within house
- 1″ nominal: Supply from water meter to house
- 1½″ nominal: Sink drain lines
- 2″ nominal: Toilet drain, main stack
- 3″ nominal: Main drain, sewer connection
- 4″ nominal: Main building drain and sewer
Copper pipe uses different sizing: Type M, L, and K copper all have the same outside diameter for a given size, but different wall thicknesses. PEX (cross-linked polyethylene) tubing uses actual measurements—1/2″ PEX has a 0.500″ outside diameter.
Weather Reporting and Climatology
United States weather forecasting measures precipitation in inches. The National Weather Service issues warnings based on inch thresholds:
- Flash Flood Watch: Expected 1-2 inches in one hour or 3-4 inches in several hours
- Heavy Snow Warning: 6+ inches in 12 hours or 8+ inches in 24 hours
- Blizzard Warning: 3+ hours of heavy snow with sustained winds 35+ mph
Rainfall intensity rates:
- Light rain: <0.10 inches per hour
- Moderate rain: 0.10 to 0.30 inches per hour
- Heavy rain: >0.30 inches per hour
Annual precipitation varies dramatically across the US:
- Las Vegas, NV: 4.2 inches per year (desert)
- Phoenix, AZ: 8.3 inches per year
- Los Angeles, CA: 14.9 inches per year
- New York, NY: 46.2 inches per year
- Seattle, WA: 37.5 inches per year
- Miami, FL: 61.9 inches per year
- Mobile, AL: 67.0 inches per year (wettest major US city)
- Mt. Waialeale, HI: 450+ inches per year (one of Earth's wettest places)
Automotive and Cycling
American automotive specifications traditionally use inches:
- Wheel Diameter: 15″, 16″, 17″, 18″, 19″, 20″, 22″ (passenger vehicles)
- Tire Width: Given in millimeters, but wheel size in inches (e.g., 225/65R17)
- Ground Clearance: Often stated in inches (e.g., 8.6″ clearance)
- Cargo Space: Cubic feet, with dimensions in inches
- Engine Displacement: Historically cubic inches (350 cu in = 5.7L), now usually liters
Bicycle sizing uses a mix of systems. Mountain bike wheels measure 26″, 27.5″ (650B), or 29″ in diameter. Road bikes use the 700c standard (approximately 27″ diameter, derived from French sizing). Frame sizes might be given in inches (17″ mountain bike) or centimeters (56cm road bike) depending on manufacturer and tradition.
HVAC and Duct Work
Heating, ventilation, and air conditioning (HVAC) systems in the US specify duct sizes in inches. Rectangular ductwork might be 6″ × 10″, 8″ × 12″, or 10″ × 16″. Round ducts come in 4″, 6″, 8″, 10″, and 12″ diameters.
Air register and vent sizes are standardized in inches:
- Floor registers: 4″ × 10″, 4″ × 12″, 4″ × 14″
- Wall registers: 6″ × 10″, 6″ × 12″, 8″ × 10″
- Return air grilles: 14″ × 24″, 16″ × 20″, 20″ × 20″
Furnace filters use inch sizing: 16″ × 20″ × 1″, 16″ × 25″ × 1″, 20″ × 25″ × 4″. The first two dimensions are the face size, and the third is the thickness. Standard filters are 1″ thick, while pleated media filters might be 4″ or 5″ thick for better filtration and airflow.
Additional Unit Information
About Foot (ft)
How many inches are in a foot?
There are exactly 12 inches in 1 foot. This relationship is fundamental to the imperial measurement system and has remained constant since ancient Roman times, when the pes (foot) was divided into 12 unciae (inches).
The 12-inch division offers mathematical convenience—12 is evenly divisible by 2, 3, 4, and 6, making fractional measurements easier in practical work. You can divide a foot into halves (6"), thirds (4"), quarters (3"), or sixths (2") with whole-number results.
Converting feet to inches: Multiply feet by 12
- 5 feet = 5 × 12 = 60 inches
- 7.5 feet = 7.5 × 12 = 90 inches
Converting inches to feet: Divide inches by 12
- 72 inches = 72 ÷ 12 = 6 feet
- 100 inches = 100 ÷ 12 = 8.33 feet = 8 feet, 4 inches
Mixed notation: 5'9" means 5 feet, 9 inches = (5 × 12) + 9 = 69 inches total.
How many feet are in a yard?
There are exactly 3 feet in 1 yard. This relationship dates back to medieval English measurements, where the yard represented a stride or the distance from the nose to an outstretched thumb of King Henry I.
The yard serves as a larger unit convenient for measuring fabric, sports fields, and medium distances. In American football, progress is measured in yards (first down = 10 yards = 30 feet), but field dimensions are often specified in feet (field width = 160 feet = 53⅓ yards).
Converting yards to feet: Multiply yards by 3
- 10 yards = 10 × 3 = 30 feet
- 100 yards = 100 × 3 = 300 feet (length of football field)
Converting feet to yards: Divide feet by 3
- 90 feet = 90 ÷ 3 = 30 yards (baseball base paths)
- 18 feet = 18 ÷ 3 = 6 yards (first down in football)
How many feet are in a mile?
There are exactly 5,280 feet in 1 mile. This seemingly arbitrary number results from historical compromises between different English measurement systems.
Historical origin: The Roman mile (mille passus) measured 1,000 paces (about 5,000 feet). Medieval England used furlongs for agricultural land measurement (660 feet = 1 furlong). Queen Elizabeth I standardized the mile in 1593 as exactly 8 furlongs, making 1 mile = 8 × 660 = 5,280 feet.
Common conversions:
- 1 mile = 5,280 feet
- 0.5 mile = 2,640 feet
- 0.25 mile = 1,320 feet
- 1,000 feet = 0.189 miles (about 3 city blocks)
Why it matters: Aircraft measure runway length in feet (7,000-foot runway, 10,000-foot runway), while navigation uses nautical miles (6,076 feet) or statute miles (5,280 feet). Real estate describes proximity in feet for nearby amenities ("500 feet to park") and miles for distant locations ("3 miles to downtown").
What's the difference between feet and square feet?
Feet (linear feet) measure distance in one dimension—length along a line. Use feet for measuring height, room length, fence lines, rope, baseboards, or any one-dimensional measurement.
Square feet measure area in two dimensions—the surface of a two-dimensional space. Use square feet for flooring, walls, ceilings, land area, or any flat surface.
The relationship: Square feet = length (in feet) × width (in feet)
- A room 12 feet long × 15 feet wide = 180 square feet
- A wall 10 feet wide × 8 feet tall = 80 square feet
Why confusion happens: A room with 54 linear feet of baseboard (12+15+12+15) contains 180 square feet of floor area. These are different measurements of the same room—perimeter versus area.
Cost implications: Contractors price differently:
- Fencing: $15-40 per linear foot installed
- Flooring: $3-12 per square foot installed
- Painting: $2-6 per square foot
Always clarify whether a price quote is per linear foot or per square foot—the difference is substantial.
Why does aviation use feet for altitude worldwide?
Aviation universally uses feet for altitude measurement, even in countries that otherwise use metric exclusively, for safety and standardization. This system was established by the International Civil Aviation Organization (ICAO) in 1947.
Historical reason: When commercial aviation developed in the 1920s-1940s, British and American manufacturers dominated, and altimeters measured in feet. As aviation became international, standardizing on the existing system proved safer and cheaper than converting all aircraft instruments and training.
Safety benefits: Universal altitude standards prevent confusion during international flights. When a French pilot, Japanese air traffic controller, and American pilot all say "flight level three-five-zero," everyone knows it means 35,000 feet. No conversion errors, no miscommunication, no accidents from unit confusion.
Vertical separation: Aircraft flying opposite directions maintain 1,000-foot vertical separation (2,000 feet above 29,000'). This separation is calibrated into procedures, training, and equipment worldwide. Changing to meters would require recalibrating countless procedures and risking lives during the transition.
Exceptions: China and Russia use meters for some domestic operations below 29,500 feet, but convert to feet-based flight levels for international flights and at high altitudes. This hybrid system is gradually shifting toward full feet-based standards.
Practical result: Pilots must understand feet regardless of nationality. Pilot training worldwide includes feet-based altitude management, making it one of the few truly universal measurements.
How do I convert feet to meters accurately?
To convert feet to meters, multiply by 0.3048. This is the exact conversion factor established by the 1959 international agreement.
Formula: meters = feet × 0.3048
Examples:
- 1 foot = 1 × 0.3048 = 0.3048 meters
- 5 feet = 5 × 0.3048 = 1.524 meters
- 6 feet = 6 × 0.3048 = 1.8288 meters
- 10 feet = 10 × 0.3048 = 3.048 meters
- 100 feet = 100 × 0.3048 = 30.48 meters
Reverse conversion (meters to feet): Divide by 0.3048, or multiply by 3.28084
- 1 meter = 1 ÷ 0.3048 = 3.28084 feet
- 5 meters = 5 × 3.28084 = 16.404 feet
- 10 meters = 10 × 3.28084 = 32.808 feet
Quick mental approximation: For rough estimates, remember 1 meter ≈ 3.3 feet (or more precisely, 3.28 feet). This gives close results:
- 10 meters ≈ 33 feet (actual: 32.8 feet)
- 100 meters ≈ 330 feet (actual: 328 feet)
For professional work requiring precision (construction, engineering, manufacturing), always use the exact factor 0.3048 rather than approximations.
What does feet-inches notation mean?
The notation 5′-9″ (or 5'9") means 5 feet, 9 inches. The single prime ′ (or apostrophe ') represents feet, while the double prime ″ (or quote ") represents inches.
Reading the notation:
- 6′ = six feet = 72 inches
- 6″ = six inches = 0.5 feet
- 5′-9″ = five feet, nine inches = 69 inches total = 5.75 feet decimal
- 12′-6½″ = twelve feet, six and a half inches = 150.5 inches = 12.542 feet decimal
Why the dash? The dash or hyphen between feet and inches makes the notation clearer in blueprints and prevents confusion. Without it, 5'9" might be misread, though the prime symbols make the meaning clear.
Common uses:
- Human height: "She's 5'6" tall"
- Room dimensions: "12' × 15' bedroom"
- Construction drawings: Wall length shown as 24'-3½"
Converting to total inches: Multiply feet by 12, then add inches:
- 5'9" = (5 × 12) + 9 = 60 + 9 = 69 inches
Converting from total inches: Divide by 12 for feet, use remainder for inches:
- 75 inches = 75 ÷ 12 = 6 remainder 3 = 6'3"
Why is the foot still used instead of meters?
The United States continues using feet instead of meters primarily due to infrastructure investment, industry standardization, and cultural identity—not because feet offer any technical advantage.
Infrastructure costs: Converting to metric would require replacing billions of feet-based measurements throughout American infrastructure:
- 4 million miles of road signs showing feet/miles
- Building codes and standards written in feet
- Millions of blueprints, survey records, and property deeds
- Construction materials sized in feet (8' studs, 4'×8' sheets)
- Manufacturing equipment calibrated in decimal feet (thousandths of an inch)
Estimated conversion cost: $370 billion to $1 trillion.
Industry standardization: American construction, real estate, aviation, and manufacturing operate entirely in feet. Changing would require:
- Retraining millions of workers
- Replacing tools, measuring devices, and equipment
- Converting countless technical documents
- Updating software systems and databases
Cultural familiarity: Americans instinctively understand feet—"six feet tall," "ten feet away," "twenty feet deep." These measurements connect to body scale and everyday experience. Most Americans don't have intuitive feel for meters, making conversion feel arbitrary and confusing.
Partial adoption: The US actually uses metric in science, medicine, military, and some industries. Soft drinks come in liters, track races use meters, pharmaceuticals dose in milligrams. Americans live in a hybrid system.
Failed conversions: The 1975 Metric Conversion Act made metric "preferred" but voluntary. Without enforcement, most industries continued with feet. Public backlash against metric road signs in the 1980s ended highway conversion attempts.
International exceptions: Aviation worldwide uses feet for altitude. Maritime navigation uses nautical miles and fathoms. Even metric countries maintain some imperial measurements in specific contexts, showing that pure metric conversion isn't always practical or necessary.
How much is an acre in feet?
One acre equals 43,560 square feet. This measurement originates from medieval English land measurement, where an acre represented the amount of land a yoke of oxen could plow in one day.
Common acre configurations:
- 1 acre = 43,560 square feet
- 1 acre ≈ 208.7 feet × 208.7 feet (if square)
- 1 acre = 660 feet × 66 feet (one furlong × one chain, historical farming measurement)
Practical examples:
- 0.25 acre = 10,890 sq ft ≈ 104.4' × 104.4' (quarter-acre suburban lot)
- 0.5 acre = 21,780 sq ft ≈ 147.6' × 147.6'
- 2 acres = 87,120 sq ft ≈ 295.2' × 295.2'
- 5 acres = 217,800 sq ft ≈ 466.7' × 466.7'
Football field comparison: An American football field including end zones measures 360 feet × 160 feet = 57,600 square feet = 1.32 acres. Without end zones, the playing field (300' × 160') is 48,000 sq ft = 1.1 acres.
Why it matters: Real estate describes land in acres but building sites in square feet or lot dimensions in feet. A half-acre lot might be 150' × 145', or 100' × 218'—multiple configurations yield the same area. Knowing the conversion helps visualize land size when shopping for property.
Zoning impact: Minimum lot sizes appear in ordinances as both acres and square feet: "0.5 acre minimum" = "21,780 square feet minimum." Subdivisions calculate density in units per acre: 4 houses per acre, 12 apartments per acre.
What's the origin of "six feet under"?
The phrase "six feet under" meaning burial or death originates from traditional grave depth—coffins were buried approximately six feet below ground surface.
Historical practice: The six-foot depth became standard in England during the 1665 Great Plague of London. Officials ordered plague victims buried "at least six foot deep" to prevent disease spread and discourage grave robbers. This depth kept odors contained and protected bodies from scavengers.
Modern burial depth: Contemporary cemeteries typically bury caskets 4-6 feet deep, though some jurisdictions specify different depths. The "six feet" measurement became culturally embedded as the standard, even when actual practice varies.
Measurement significance: Six feet provides enough earth to protect the coffin from surface disturbance (weather, animals, agriculture) while remaining practical to dig manually. Deeper burials exponentially increase labor, while shallower burials risk exposure.
Cultural persistence: The phrase "six feet under" persists in English as a euphemism for death, demonstrating how foot-based measurements embedded themselves in language and culture beyond mere physical measurement.
About Inch (in)
How many inches are in a foot?
There are exactly 12 inches in one foot. This relationship is fixed by definition in the US customary and imperial systems. The division of a foot into 12 parts dates back to ancient Roman measurements and remained standard because 12 is easily divisible by 2, 3, 4, and 6—making fractional measurements convenient in practical applications.
To convert feet to inches, multiply by 12. To convert inches to feet, divide by 12.
- 5 feet = 5 × 12 = 60 inches
- 48 inches = 48 ÷ 12 = 4 feet
- 3 feet 7 inches = (3 × 12) + 7 = 43 inches total
How many centimeters are in an inch?
One inch equals exactly 2.54 centimeters. This relationship was established by the 1959 international yard and pound agreement, which defined the yard as exactly 0.9144 meters. Since one inch equals 1/36 of a yard, it works out to precisely 2.54 cm.
This is one of the few perfectly defined relationships between imperial and metric systems. There's no rounding or approximation—it's exactly 2.54000... cm per inch by international agreement.
To convert inches to centimeters, multiply by 2.54. To convert centimeters to inches, divide by 2.54.
- 10 inches = 10 × 2.54 = 25.4 cm
- 50 cm = 50 ÷ 2.54 = 19.685 inches
Why does the US still use inches instead of the metric system?
The United States remains one of only three countries (along with Myanmar and Liberia) not officially using the metric system, largely due to historical momentum, infrastructure costs, and cultural identity.
Infrastructure Investment: The US has trillions of dollars invested in imperial-based infrastructure—road signs showing miles, construction materials in feet and inches, manufacturing equipment calibrated in thousandths of an inch, pipelines in inch diameters, and billions of blueprints in feet-inches notation. Converting all of this would cost an estimated $370 billion to $1 trillion.
Industry Standardization: American manufacturing, construction, and engineering have perfected systems around imperial measurements over centuries. Millions of workers are trained in inches and feet. Changing would require retraining entire industries and replacing countless tools, gauges, and documentation.
Cultural Resistance: Americans intuitively understand inches, feet, and miles from childhood. Polls consistently show that most Americans oppose mandatory metric conversion, viewing it as unnecessary government overreach. Unlike temperature (where Fahrenheit provides finer granularity for weather), length measurements in inches don't provide any practical advantage—but changing feels like abandoning tradition.
Failed Conversion Attempts: Congress passed the Metric Conversion Act in 1975, making metric the "preferred system" but keeping adoption voluntary. Without enforcement, industries continued using imperial. A 1982 push to convert road signs to kilometers was abandoned after fierce public backlash.
Partial Adoption: The US actually uses metric extensively in science, medicine, military, and some industries. All US customary units are now legally defined in terms of metric units. Americans live in a hybrid system—drinking 2-liter sodas while driving 65 miles per hour.
What's the difference between decimal inches and fractional inches?
Fractional inches express measurements as common fractions: 1/2″, 3/4″, 5/8″, 7/16″, 15/32″. This system dominates carpentry, construction, and mechanical work. Rulers and tape measures show fraction markings—typically down to 1/16″ for standard use and 1/32″ for precision carpentry.
Decimal inches express measurements as decimal values: 0.5″, 0.75″, 0.625″, 0.4375″, 0.46875″. Engineering drawings, machining, and manufacturing prefer decimals because they're easier to calculate with, especially for tolerances and fits.
Both systems describe the same measurements:
- 1/2″ = 0.500″
- 3/4″ = 0.750″
- 5/8″ = 0.625″
- 1/8″ = 0.125″
Machine shops often work in "thousandths" (0.001″, called a "thou" or "mil") for precision. A machinist might drill a 0.257″ diameter hole—trying to express this as a fraction (257/1000″) would be impractical.
Carpenters and builders work in fractions because tape measures show fractions, and because halving measurements repeatedly (1/2, 1/4, 1/8, 1/16, 1/32) is natural in layout work.
How accurate is an inch measurement?
The definition of an inch is exact: 2.54 centimeters precisely, or 25.4 millimeters. There's no uncertainty in the standard itself.
Practical accuracy depends on the measuring tool:
- Ruler or tape measure: Accurate to roughly ±1/16″ (±1.6 mm) for careful work
- Steel ruler with machinist's markings: ±1/32″ (±0.8 mm) when read carefully
- Dial calipers: ±0.001″ (±0.025 mm) typical accuracy
- Digital calipers: ±0.0005″ (±0.013 mm) for quality instruments
- Micrometers: ±0.0001″ (±0.0025 mm) for precision tools
- Coordinate measuring machines (CMM): ±0.00005″ (±0.0013 mm) or better
Different trades require different precision:
- House framing: ±1/8″ is usually acceptable
- Finish carpentry: ±1/16″ or better for visible joints
- Cabinetmaking: ±1/32″ for tight-fitting doors and drawers
- Machining: ±0.001″ (one thousandth) for standard fits
- Precision machining: ±0.0001″ (one ten-thousandth, called a "tenth")
- Gauge blocks (calibration standards): Accurate to millionths of an inch
Can I use a metric wrench on an inch bolt?
Generally no—metric and imperial fasteners are incompatible. While some sizes appear close, using the wrong wrench damages bolt heads and nuts.
Why they're incompatible: Metric sockets and wrenches are sized in millimeters (8mm, 10mm, 13mm, 17mm), while imperial fasteners use fractional inches (5/16″, 3/8″, 1/2″, 5/8″). These don't align:
- 13mm = 0.512″ (close to 1/2″ = 0.500″, but not exact)
- 10mm = 0.394″ (between 3/8″ = 0.375″ and 7/16″ = 0.438″)
The result: A 13mm wrench on a 1/2″ bolt will be 0.012″ too large—enough to round off the hex corners with sufficient force. A 10mm wrench on a 3/8″ bolt won't fit at all.
Exception: In an emergency, you might carefully use a slightly large adjustable wrench or locking pliers, but this risks damaging the fastener. Always use the correct system—if you work on American-made equipment, you need inch tools. For European or Japanese equipment, you need metric tools.
Many professional mechanics maintain complete sets of both imperial and metric sockets, wrenches, and hex keys—a significant investment but essential for working on diverse equipment.
What does the ″ symbol mean?
The double prime symbol ″ represents inches in technical drawings, blueprints, and mathematical contexts. A single prime ′ represents feet.
Standard notation:
- 5′ = five feet
- 5″ = five inches
- 5′-3″ = five feet, three inches
- 5′-3½″ = five feet, three and a half inches
Origin: These symbols come from astronomical and geometric notation, where they represented divisions of degrees (°). A degree divided by 60 gives minutes (′), and a minute divided by 60 gives seconds (″). This notation was borrowed for feet and inches because of the similar subdividing relationship.
Common substitution: Because typewriters and keyboards lack easy access to proper prime symbols, people often substitute:
- Apostrophe (') for feet: 5' tall
- Quotation mark (") for inches: 5" wide
- Both together: 5'-3" tall
In professional CAD drawings and blueprints, proper prime symbols (′ and ″) are standard. In casual writing, apostrophes and quotes are acceptable and universally understood.
How is screen size measured in inches?
Display screen sizes (TVs, monitors, tablets, smartphones) are always measured diagonally from one corner to the opposite corner, measuring only the visible screen area (not the bezel or frame).
Why diagonal? This convention originated with cathode ray tubes (CRTs), where the diagonal measurement corresponded to the size of the round tube face. When rectangular screens became standard, the diagonal measurement convention persisted for consistency.
Practical dimensions for common sizes:
TVs (16:9 aspect ratio):
- 55″ diagonal = approximately 48″ wide × 27″ tall
- 65″ diagonal = approximately 56.7″ wide × 31.9″ tall
- 75″ diagonal = approximately 65.4″ wide × 36.8″ tall
Monitors (16:9 aspect ratio):
- 24″ diagonal = approximately 20.9″ wide × 11.8″ tall
- 27″ diagonal = approximately 23.5″ wide × 13.2″ tall
Why this matters: When planning where to place a TV or monitor, you need the actual width and height, not the diagonal. Always check specifications for exact dimensions. Also add 1-2 inches in each direction to account for the bezel.
How do I convert inches to millimeters?
To convert inches to millimeters, multiply by 25.4. This gives you an exact result because the inch is legally defined as exactly 2.54 centimeters (25.4 millimeters).
Formula: millimeters = inches × 25.4
Examples:
- 1 inch = 1 × 25.4 = 25.4 mm
- 2 inches = 2 × 25.4 = 50.8 mm
- 0.5 inches = 0.5 × 25.4 = 12.7 mm
- 10 inches = 10 × 25.4 = 254 mm
- 3.25 inches = 3.25 × 25.4 = 82.55 mm
Converting fractional inches: First convert the fraction to a decimal, then multiply by 25.4:
- 1/2″ = 0.5″ = 0.5 × 25.4 = 12.7 mm
- 3/4″ = 0.75″ = 0.75 × 25.4 = 19.05 mm
- 5/8″ = 0.625″ = 0.625 × 25.4 = 15.875 mm
- 1/8″ = 0.125″ = 0.125 × 25.4 = 3.175 mm
Reverse conversion (mm to inches): Divide millimeters by 25.4:
- 50 mm = 50 ÷ 25.4 = 1.969 inches (approximately 2 inches)
- 100 mm = 100 ÷ 25.4 = 3.937 inches (approximately 4 inches)
For quick mental estimates, remember that 25mm ≈ 1 inch. This gives you approximately correct values for rough planning, though it slightly underestimates (25mm is actually 0.984 inches).
Why are lumber dimensions not the actual size?
Lumber in the United States is sold using nominal dimensions—traditional names that don't match the actual milled size. A "2×4" is actually 1.5″ × 3.5″, not 2″ × 4″.
Historical reason: Originally, rough-cut lumber fresh from the sawmill did measure 2″ × 4″. However, the lumber then went through drying (removing moisture) and planing (smoothing surfaces), which reduced dimensions by approximately 1/4″ on each face. Rather than rename everything, the industry kept nominal sizing for ordering convenience while standardizing actual dimensions.
Standard actual dimensions:
- 2×4 → 1.5″ × 3.5″
- 2×6 → 1.5″ × 5.5″
- 2×8 → 1.5″ × 7.25″
- 2×10 → 1.5″ × 9.25″
- 2×12 → 1.5″ × 11.25″
- 4×4 → 3.5″ × 3.5″
- 1×4 → 0.75″ × 3.5″
- 1×6 → 0.75″ × 5.5″
These dimensions are mandated by the American Softwood Lumber Standard (PS 20-20) and are consistent across all retailers.
Why this system persists: Construction is designed around nominal dimensions. Studs are spaced "16 inches on center" in walls, but everyone understands the actual stud is 1.5″ thick. Changing to actual dimension naming would require rewriting building codes, retraining millions of workers, and changing century-old industry conventions.
Important for DIY: Always design projects using actual lumber dimensions, not nominal. If you're building something that needs to be exactly 4 inches wide, a 2×4 laid flat won't work—it's only 3.5 inches.
What is the smallest measurement on a standard tape measure?
Most standard tape measures used in construction and carpentry show markings down to 1/16 inch as the smallest division. Each inch is divided into 16 equal parts, with various line lengths to indicate fractions:
- Longest lines: Every inch (1″, 2″, 3″...)
- Next longest: Half inches (1/2″, 1½″, 2½″...)
- Medium lines: Quarter inches (1/4″, 3/4″, 1¼″...)
- Shorter lines: Eighths (1/8″, 3/8″, 5/8″, 7/8″)
- Shortest lines: Sixteenths (1/16″, 3/16″, 5/16″... through 15/16″)
Precision tape measures for finish carpentry may show 1/32-inch divisions, doubling the number of marks. These are harder to read but provide twice the precision for fine woodworking.
Reading tape measures: The marks use a graduated system where longer marks indicate simpler fractions. The 1/2″ mark is the longest subdivision line, the 1/4″ and 3/4″ marks are slightly shorter, the 1/8″ marks are shorter still, and the 1/16″ marks are the shortest. This visual hierarchy makes it easier to count marks and identify positions quickly without having to count every line.
Practical accuracy: Even with 1/16″ markings, human error in marking and cutting typically limits practical accuracy to about ±1/16″ for construction work. Finish carpentry might achieve ±1/32″ with careful measurement and sharp marking.
For measurements more precise than 1/32 inch, professionals use dial calipers (readable to 0.001″) or digital calipers rather than tape measures.
Conversion Table: Foot to Inch
| Foot (ft) | Inch (in) |
|---|---|
| 0.5 | 6 |
| 1 | 12 |
| 1.5 | 18 |
| 2 | 24 |
| 5 | 60 |
| 10 | 120 |
| 25 | 300 |
| 50 | 600 |
| 100 | 1,200 |
| 250 | 3,000 |
| 500 | 6,000 |
| 1,000 | 12,000 |
People Also Ask
How do I convert Foot to Inch?
To convert Foot to Inch, enter the value in Foot in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our length converter page to convert between other units in this category.
Learn more →What is the conversion factor from Foot to Inch?
The conversion factor depends on the specific relationship between Foot and Inch. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.
Can I convert Inch back to Foot?
Yes! You can easily convert Inch back to Foot by using the swap button (⇌) in the calculator above, or by visiting our Inch to Foot converter page. You can also explore other length conversions on our category page.
Learn more →What are common uses for Foot and Inch?
Foot and Inch are both standard units used in length measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our length converter for more conversion options.
For more length conversion questions, visit our FAQ page or explore our conversion guides.
Helpful Conversion Guides
Learn more about unit conversion with our comprehensive guides:
📚 How to Convert Units
Step-by-step guide to unit conversion with practical examples.
🔢 Conversion Formulas
Essential formulas for length and other conversions.
⚖️ Metric vs Imperial
Understand the differences between measurement systems.
⚠️ Common Mistakes
Learn about frequent errors and how to avoid them.
All Length Conversions
Other Length Units and Conversions
Explore other length units and their conversion options:
- Meter (m) • Foot to Meter
- Kilometer (km) • Foot to Kilometer
- Hectometer (hm) • Foot to Hectometer
- Decimeter (dm) • Foot to Decimeter
- Centimeter (cm) • Foot to Centimeter
- Millimeter (mm) • Foot to Millimeter
- Yard (yd) • Foot to Yard
- Mile (mi) • Foot to Mile
- Nautical Mile (NM) • Foot to Nautical Mile
- Micrometer (μm) • Foot to Micrometer
Verified Against Authority Standards
All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — Official US standards for length measurements
Bureau International des Poids et Mesures — International System of Units official documentation
Last verified: December 3, 2025