Foot to Parsec Converter
Convert feet to parsecs with our free online length converter.
Quick Answer
1 Foot = 9.877824e-18 parsecs
Formula: Foot × conversion factor = Parsec
Use the calculator below for instant, accurate conversions.
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All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.
Foot to Parsec Calculator
How to Use the Foot to Parsec Calculator:
- Enter the value you want to convert in the 'From' field (Foot).
- The converted value in Parsec 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 Parsec: Step-by-Step Guide
Converting Foot to Parsec involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Foot = 9.8778e-18 parsecsExample Calculation:
Convert 10 feet: 10 × 9.8778e-18 = 9.8778e-17 parsecs
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
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View all Length conversions →What is a Foot and a Parsec?
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.
and Standards
Geometric Definition
The parsec is defined through trigonometric parallax:
1 parsec = the distance at which 1 astronomical unit (AU) subtends an angle of 1 arcsecond (1″)
Mathematically:
- 1 parsec = 1 AU / tan(1″)
- Since 1″ = 1/3600 degree = π/648,000 radians ≈ 4.8481 × 10⁻⁶ radians
- For small angles: tan(θ) ≈ θ (in radians)
- 1 parsec ≈ 1 AU / 4.8481 × 10⁻⁶ ≈ 206,265 AU
Exact IAU Value
The International Astronomical Union (IAU) defines the parsec exactly as:
1 parsec = 648,000/π AU ≈ 206,264.806247 AU
Using the IAU-defined astronomical unit (1 AU = 149,597,870,700 meters exactly as of 2012):
1 parsec = 30,856,775,814,913,673 meters (exactly)
Or approximately:
- 3.0857 × 10¹⁶ meters
- 30.857 trillion kilometers
- 19.174 trillion miles
Relationship to Light-Year
The light-year (distance light travels in one Julian year) relates to the parsec:
1 parsec ≈ 3.26156 light-years
More precisely: 1 pc = 3.261563777 ly (using Julian year of 365.25 days)
Standard Multiples
Kiloparsec (kpc): 1 kpc = 1,000 pc ≈ 3,262 ly
- Used for distances within galaxies
- Milky Way diameter: ~30 kpc
Megaparsec (Mpc): 1 Mpc = 1,000,000 pc ≈ 3.26 million ly
- Used for intergalactic distances
- Andromeda Galaxy: ~0.77 Mpc
Gigaparsec (Gpc): 1 Gpc = 1,000,000,000 pc ≈ 3.26 billion ly
- Used for cosmological distances
- Observable universe radius: ~14 Gpc
Note: The Foot is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Parsec belongs to the imperial/US customary system.
History of the Foot and Parsec
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.
and Evolution
Pre-Parsec Era: The Parallax Quest (1600s-1830s)
The concept of stellar parallax dates to ancient Greek astronomy, but detecting it required centuries of technological advancement.
Galileo Galilei (1610) suggested that if Earth orbits the Sun, nearby stars should show annual parallax shifts against distant background stars. No parallax was detected, leading geocentrists to argue Earth must be stationary.
James Bradley (1728) discovered stellar aberration (apparent star position shifts due to Earth's orbital motion combined with finite light speed), confirming Earth's motion but still failing to detect parallax—stars were simply too distant.
Friedrich Wilhelm Bessel achieved the first successful parallax measurement in 1838 for 61 Cygni, determining a distance of about 10.3 light-years (3.16 parsecs, though the term didn't exist yet). This triumph came using a heliometer—a split-lens telescope enabling precise angular measurements.
Thomas Henderson measured Alpha Centauri's parallax (1832-1833, published 1839), and Friedrich Struve measured Vega's (1837), establishing parallax as the fundamental distance measurement method.
Coining the Term (1913)
Herbert Hall Turner (1861-1930), British astronomer and director of Oxford University Observatory, coined "parsec" in 1913. Before this, astronomers expressed stellar distances awkwardly:
- In astronomical units (requiring numbers in the hundreds of thousands)
- In light-years (popular but not directly tied to measurement method)
- In "parallax seconds" (inverse of parallax angle, but confusing terminology)
Turner recognized that astronomers naturally thought in terms of parallax angles. For a star with parallax angle p (in arcseconds), the distance d is simply:
d (in parsecs) = 1 / p (in arcseconds)
This elegant relationship made the parsec immediately practical. A star with 0.5″ parallax is 2 parsecs away; 0.1″ parallax means 10 parsecs; 0.01″ parallax means 100 parsecs.
IAU Adoption (1922-1938)
The 1922 IAU General Assembly in Rome endorsed the parsec as the standard unit for stellar distances, though adoption wasn't immediate or universal.
The 1938 IAU General Assembly in Stockholm formally standardized the parsec definition based on the astronomical unit and arcsecond, solidifying its status.
By the 1950s, the parsec dominated professional astronomy literature, though popular science continued preferring light-years for general audiences.
Space Age Precision (1960s-Present)
Hipparcos satellite (1989-1993): European Space Agency mission measured parallaxes for 118,000 stars with milliarcsecond precision, extending reliable parsec-based distances to hundreds of parsecs.
Gaia mission (2013-present): ESA's Gaia spacecraft has revolutionized astrometry, measuring parallaxes for 1.8 billion stars with microarcsecond precision. This extends direct parsec measurements to 10,000+ parsecs (10+ kiloparsecs), mapping our galaxy's structure in unprecedented detail.
2012 IAU redefinition: The IAU redefined the astronomical unit as exactly 149,597,870,700 meters (no longer based on Earth's actual orbit, which varies slightly). This made the parsec exactly 648,000/π AU, providing a stable definition independent of Earth's orbital variations.
Common Uses and Applications: feet vs parsecs
Explore the typical applications for both Foot (imperial/US) and Parsec (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 parsecs
Stellar Astronomy and Parallax Measurements
The parsec's primary use is measuring stellar distances via trigonometric parallax:
Parallax formula: d (parsecs) = 1 / p (arcseconds)
Ground-based observatories: Measure parallaxes to ~0.01″ accuracy, reliable to ~100 pc
Hipparcos satellite: Measured parallaxes to ~0.001″ (1 milliarcsecond), reliable to ~1,000 pc (1 kpc)
Gaia spacecraft: Measures parallaxes to ~0.00001″ (10 microarcseconds) for bright stars, reliable to ~10 kpc for many stars
Applications:
- Calibrating the cosmic distance ladder (using Cepheid variables, RR Lyrae stars)
- Determining absolute magnitudes of stars
- Studying stellar populations and galactic structure
- Measuring proper motions and space velocities
Galactic Structure and Dynamics
Kiloparsecs (kpc) describe structures within galaxies:
Milky Way structure:
- Galactic center (Sagittarius A*): 8.2 kpc from Sun
- Galactic disk radius: ~15 kpc
- Central bulge: ~1.5 kpc radius
- Spiral arms: trace patterns 10-15 kpc in radius
- Dark matter halo: extends to ~60 kpc
Rotation curves: Plot orbital velocity vs. distance (in kpc) from galactic center, revealing dark matter
Star formation regions: Giant molecular clouds span 10-100 pc
Globular clusters: Orbit 10-60 kpc from galactic center
Extragalactic Astronomy
Megaparsecs (Mpc) measure distances between galaxies:
Galaxy surveys: Map millions of galaxies to distances of 1,000+ Mpc, revealing large-scale structure (walls, filaments, voids)
Tully-Fisher relation: Links galaxy rotation speed to luminosity, enabling distance estimates in Mpc
Type Ia supernovae: Standard candles for measuring distances to 1,000+ Mpc
Galaxy clusters: Typical separation between major clusters ~10-50 Mpc
Superclusters: Structures spanning 100-200 Mpc (like Laniakea Supercluster containing Milky Way)
Cosmology and Universe Expansion
Megaparsecs and gigaparsecs describe cosmological distances:
Hubble constant (H₀): Measured in km/s per Mpc—describes universe expansion rate
- Current value: H₀ ≈ 67-73 (km/s)/Mpc (tension between measurement methods)
- Interpretation: Galaxy 1 Mpc away recedes at ~70 km/s; 100 Mpc away recedes at ~7,000 km/s
Hubble's Law: v = H₀ × d (where d is in Mpc, v is recession velocity)
Comoving distance: Cosmological distance accounting for universe expansion, measured in Mpc or Gpc
Redshift surveys: Map galaxy distribution to 1,000+ Mpc (z ~ 0.1-0.3 redshift)
Baryon acoustic oscillations: ~150 Mpc characteristic scale in galaxy distribution, used as "standard ruler"
Astrophysical Research Papers
Parsecs are the default distance unit in professional astronomy journals:
Observational papers: Report star/galaxy distances in pc, kpc, or Mpc
Theoretical models: Express scale lengths in parsecs (e.g., "disk scale length of 3 kpc")
Computer simulations: Use parsec-based units (or comoving kpc/Mpc for cosmological sims)
Standard convention: Professional astronomers think and calculate in parsecs, converting to light-years only for public communication
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 fast does light travel in a foot?
In vacuum, light travels one foot in approximately 1.0167 nanoseconds. In computer networking and high-frequency trading, this is a critical measurement—engineers often say "a nanosecond is a foot" as a rule of thumb for how fast signals move through cables.
Why is a "foot" divided into 12 inches instead of 10?
The number 12 is a "Highly Composite Number." It can be divided evenly into 2, 3, 4, and 6. This was incredibly useful for ancient builders and tradesmen who didn't have calculators. They could easily calculate "half a foot" (6"), "a third of a foot" (4"), or "a quarter of a foot" (3") without dealing with decimals like 3.333.
Is my physical foot actually one foot long?
Probably not! The average male foot is about 10.5 inches (26.6 cm) long, and the average female foot is about 9.5 inches (24 cm). The "standard foot" measurement was likely based on a very large foot (perhaps a king's) or a foot wearing a heavy boot.
What is the "Board Foot" used in lumber?
A board foot is actually a unit of volume, not length. It represents a piece of wood that is 1 foot long, 1 foot wide, and 1 inch thick. When you buy expensive hardwood, the price is usually "per board foot."
How many feet are in a "Standard Story" of a building?
In residential construction, a floor is typically 8 to 10 feet high. In commercial office buildings, it's often 12 to 14 feet to allow for air conditioning ducts and wiring above the ceiling.
Can a pilot choose to fly in meters?
No. In almost every country in the world, air traffic control mandates the use of feet for altitude. If a pilot used meters, they might collide with another plane. The only major exceptions have historically been Russia and China, and even they are moving toward the international feet-based standard.
What is a "Square Foot" vs. a "Linear Foot"?
Linear feet measure length (like a fence). Square feet measure area (like a carpet). A 10' x 10' room has 40 linear feet of walls but 100 square feet of floor.
Is the UK foot different from the US foot?
Since 1959, they are identical. Before 1959, the UK foot was about 2 parts per million shorter than the US foot.
How many feet are in a Fathom?
A Fathom is exactly 6 feet. It was traditionally the distance between a man's outstretched arms and is still used today to measure water depth in maritime navigation.
Why do we use a prime mark (') for feet?
The single prime (') comes from the Latin minuta, meaning "small part." The double prime (") for inches comes from secunda minuta, or "second small part." Interestingly, this is the same reason we use these symbols for minutes and seconds in time!
How many feet are in a "Rod"?
A rod is a historical unit of length equal to 16.5 feet. It was used in land surveying because four rods equal one "chain" (66 feet), and 80 chains equal exactly one mile.
What is the "Cubic Foot" of a refrigerator?
In the US, appliance capacity is measured in cubic feet. A 20 cubic foot refrigerator can hold approximately 566 liters of food. This is the volume of a space 1 foot high, 1 foot wide, and 1 foot deep, multiplied by 20.
How many feet is the world's deepest ocean point?
The Challenger Deep in the Mariana Trench is approximately 35,876 feet (10,935 meters) below sea level. If you put Mount Everest (29,032 feet) inside it, there would still be over a mile of water above the peak.
Why do some rulers have "architect's scales" in feet?
Architect's rulers allow you to draw large buildings on small paper. A common scale is 1/4 inch = 1 foot. This means every quarter-inch mark on your drawing represents 12 inches of a real building.
How many feet is a "Standard Leap" in the Long Jump?
The world record for the men's long jump is 29 feet, 4.25 inches (8.95 meters), set by Mike Powell in 1991.
Can I calculate feet by counting my steps?
Yes! A standard walking step (pace) for an adult is roughly 2.5 feet. If you count 40 steps, you have walked approximately 100 feet.
How many feet is an Olympic Swimming Pool?
A standard Olympic pool is 50 meters long, which is approximately 164 feet. In the US, many high school and community pools are "short course," meaning they are exactly 25 yards (75 feet) or 25 meters (82 feet).
What is a "Square Foot" of leather?
Tanneries sell leather by the square foot. Because hide shapes are irregular, specialized machines "scan" the skin to calculate the total square footage for pricing.
Is the "Metric Foot" a real thing?
Unofficially, yes. In some metric countries transitioning away from imperial units, builders sometimes use a "Metric Foot" of exactly 30 centimeters. It is roughly 1.5% shorter than a real foot but makes decimal math easier on construction sites.
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 Parsec (pc)
What does "parsec" stand for?
Parsec is a portmanteau of "parallax of one arcsecond."
It represents the distance at which Earth's orbital radius (1 AU) subtends an angle of exactly one arcsecond (1/3600 of a degree). British astronomer Herbert Hall Turner coined the term in 1913 to provide a convenient unit directly tied to the parallax measurement method.
How is a parsec measured?
Parsecs are measured using trigonometric parallax:
- Observe a nearby star from Earth when Earth is on one side of its orbit
- Observe the same star six months later when Earth is on the opposite side
- Measure the apparent shift in the star's position against distant background stars
- Half this shift is the parallax angle p (in arcseconds)
- Calculate distance: d = 1/p parsecs
Modern method: Space telescopes like Gaia measure parallax angles with microarcsecond precision, enabling distance measurements to thousands of parsecs.
Is a parsec bigger than a light-year?
Yes, one parsec is significantly larger:
1 parsec ≈ 3.26 light-years
More precisely: 1 pc = 3.261563777 ly
Example: Proxima Centauri at 1.3 parsecs equals 4.24 light-years away.
Why the difference matters: Confusing parsecs with light-years introduces 3× error in distances.
Why do astronomers prefer parsecs over light-years?
Astronomers prefer parsecs for several reasons:
1. Direct observational connection: Parallax angle p (arcseconds) directly gives distance d = 1/p (parsecs). No complicated conversion needed.
2. Professional standard: IAU endorsed parsecs in 1922; they're now universal in research papers and textbooks.
3. Convenient multiples: Kiloparsecs (kpc) for galactic distances, megaparsecs (Mpc) for cosmological distances provide natural scales.
4. Hubble constant units: Universe expansion rate naturally expressed in (km/s)/Mpc.
5. Definition stability: Light-year depends on year length definition (tropical, Julian, sidereal); parsec defined purely by geometry.
Light-years remain popular in public communication because "year" is familiar, while "parallax arcsecond" requires technical knowledge.
How many astronomical units are in a parsec?
1 parsec = 206,265 astronomical units (AU) (approximately)
More precisely: 1 pc = 206,264.806247 AU
This number arises from: 1 pc = 1 AU / tan(1″), and since 1″ = π/648,000 radians:
- 1 pc = 1 AU / (π/648,000) = 648,000/π AU ≈ 206,265 AU
Context: Since 1 AU ≈ 150 million km (Earth-Sun distance), 1 parsec ≈ 31 trillion km.
What is a kiloparsec and megaparsec?
Kiloparsec (kpc): 1 kpc = 1,000 parsecs ≈ 3,262 light-years
- Used for: Galactic-scale distances
- Examples: Sun to Milky Way center (8 kpc), galaxy diameters (10-50 kpc)
Megaparsec (Mpc): 1 Mpc = 1,000,000 parsecs ≈ 3.26 million light-years
- Used for: Intergalactic distances, cosmology
- Examples: Andromeda Galaxy (0.77 Mpc), Virgo Cluster (16.5 Mpc), Hubble constant measured in (km/s)/Mpc
Gigaparsec (Gpc): 1 Gpc = 1,000,000,000 parsecs ≈ 3.26 billion light-years
- Used for: Large-scale cosmological structures
- Example: Observable universe radius (~14 Gpc)
Is the parsec an SI unit?
No, the parsec is not an SI unit. The SI unit of length is the meter (m).
However, the parsec is:
- Recognized by the IAU (International Astronomical Union)
- Accepted for use with SI in astronomy contexts
- Defined exactly in terms of the AU (which is defined exactly in meters)
Why not SI?: The parsec arose naturally from astronomical practice and remains far more practical than expressing stellar distances in meters (which would require numbers like 10¹⁶ to 10²³).
Analogy: Like the electronvolt (eV) in particle physics, the parsec is a specialized unit indispensable to its field despite not being SI.
How far can parallax measure distances?
Ground-based telescopes: ~0.01 arcsecond precision → reliable to ~100 parsecs
Hubble Space Telescope: ~0.001 arcsecond (1 milliarcsecond) → reliable to ~1,000 parsecs (1 kpc)
Hipparcos satellite (1989-1993): ~0.001 arcsecond → 118,000 stars measured to 100-1,000 pc
Gaia spacecraft (2013-present): ~0.00001 arcsecond (10 microarcseconds) for bright stars → reliable to ~10,000 parsecs (10 kpc)
- Measured 1.8 billion stars
- Revolutionary precision enables mapping entire Milky Way disk
Fundamental limit: Stars beyond 10-20 kpc have unmeasurably small parallaxes with current technology. For greater distances, astronomers use indirect methods (Cepheids, Type Ia supernovae, redshift).
Did Han Solo make the Kessel Run in "less than 12 parsecs"?
Famous Star Wars quote: "She made the Kessel Run in less than twelve parsecs."
The issue: Parsec measures distance, not time. Saying "less than 12 parsecs" for a speed achievement is like saying "I drove to work in less than 5 miles."
Fan explanations (retroactive justifications):
- The Kessel Run involves navigating near black holes; a shorter distance means a more dangerous, direct route
- Skilled pilots can shave distance by flying closer to gravitational hazards
- This reinterprets "12 parsecs" as boasting about route optimization, not speed
Real answer: George Lucas likely confused parsecs with a time unit when writing the script. The line became famous enough that later writers invented explanations making it technically correct.
Takeaway: In real astronomy, parsecs always measure distance, never time.
How do parsecs relate to the Hubble constant?
The Hubble constant (H₀) describes universe expansion and is typically expressed as:
H₀ ≈ 70 (km/s)/Mpc
Interpretation: For every megaparsec of distance, recession velocity increases by ~70 km/s.
Examples using Hubble's Law (v = H₀ × d):
- Galaxy 1 Mpc away: recedes at ~70 km/s
- Galaxy 10 Mpc away: recedes at ~700 km/s
- Galaxy 100 Mpc away: recedes at ~7,000 km/s
- Galaxy 1,000 Mpc away: recedes at ~70,000 km/s
Hubble length: c/H₀ ≈ 4,400 Mpc (14.4 billion ly) - characteristic distance scale of observable universe
Why Mpc?: Using megaparsecs keeps Hubble constant values convenient (70 rather than 0.000000000070 if using parsecs, or 2.3 × 10⁻¹⁸ if using SI meters).
What's the farthest distance ever measured in parsecs?
Observable universe radius: ~14,000 Mpc = 14 Gpc (46 billion light-years comoving distance)
Most distant galaxy observed (as of 2023): JADES-GS-z13-0 at redshift z ≈ 13.2
- Comoving distance: ~4,200 Mpc (13.7 billion light-years light-travel distance)
- Due to universe expansion, it's now ~10,000 Mpc (32 billion light-years) away
Cosmic microwave background: Emitted 380,000 years after Big Bang
- Comoving distance to CMB surface: ~14,000 Mpc (46 billion light-years)
Beyond measurement: The observable universe has a finite size (~14 Gpc radius) due to finite age and light speed. Objects beyond this "cosmological horizon" are unobservable because their light hasn't reached us yet.
Conversion Table: Foot to Parsec
| Foot (ft) | Parsec (pc) |
|---|---|
| 0.5 | 0 |
| 1 | 0 |
| 1.5 | 0 |
| 2 | 0 |
| 5 | 0 |
| 10 | 0 |
| 25 | 0 |
| 50 | 0 |
| 100 | 0 |
| 250 | 0 |
| 500 | 0 |
| 1,000 | 0 |
People Also Ask
How do I convert Foot to Parsec?
To convert Foot to Parsec, 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 Parsec?
The conversion factor depends on the specific relationship between Foot and Parsec. 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 Parsec back to Foot?
Yes! You can easily convert Parsec back to Foot by using the swap button (⇌) in the calculator above, or by visiting our Parsec to Foot converter page. You can also explore other length conversions on our category page.
Learn more →What are common uses for Foot and Parsec?
Foot and Parsec 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.
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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
- Inch (in) • Foot to Inch
- Yard (yd) • Foot to Yard
- Mile (mi) • Foot to Mile
- Nautical Mile (NM) • Foot to Nautical Mile
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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
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Last verified: February 19, 2026