Kilometer per hour to Foot per second Converter
Convert kilometers per hour to feet per second with our free online speed converter.
Quick Answer
1 Kilometer per hour = 0.911344 feet per second
Formula: Kilometer per hour × conversion factor = Foot per second
Use the calculator below for instant, accurate conversions.
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Kilometer per hour to Foot per second Calculator
How to Use the Kilometer per hour to Foot per second Calculator:
- Enter the value you want to convert in the 'From' field (Kilometer per hour).
- The converted value in Foot per second will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Speed category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Kilometer per hour to Foot per second: Step-by-Step Guide
Converting Kilometer per hour to Foot per second involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Kilometer per hour = 0.911344 feet per secondExample Calculation:
Convert 60 kilometers per hour: 60 × 0.911344 = 54.68066 feet per second
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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Need to convert to other speed units?
View all Speed conversions →What is a Kilometer per hour and a Foot per second?
Kilometers per hour (km/h or kph) is a unit of speed expressing the number of kilometers traveled in one hour.
Mathematical definition:
- 1 km/h = 1 kilometer ÷ 1 hour
- 1 km/h = 1,000 meters ÷ 3,600 seconds
- 1 km/h = 0.277777... meters per second (exactly 5/18 m/s)
Exact conversions:
- 1 km/h = 0.621371192 miles per hour (mph)
- 1 mph = 1.609344 km/h (exact, by international agreement)
- 1 km/h = 0.539956803 knots
- 1 km/h = 0.911344415 feet per second
km/h vs. kph: Which is Correct?
Both symbols are used, but km/h is officially preferred:
km/h (preferred):
- Official ISO 80000 standard notation
- Recommended by International Bureau of Weights and Measures (BIPM)
- Used in scientific literature, official road signs in most countries
- Visually clearer: explicitly shows "kilometers" and "hour"
kph (informal):
- Common in casual conversation and older signage
- Shorter and quicker to type
- Still widely understood globally
- Used by some speedometer manufacturers
In practice: Road signs in most countries use "km/h," but people often say "kph" when speaking. Both are universally understood, and you'll never cause confusion using either.
and Standards
The foot per second is defined as:
US Customary Definition
1 ft/s = the velocity of a body that travels a distance of one foot in a time interval of one second.
Formula: v (ft/s) = distance (feet) / time (seconds)
Exact SI conversion (since 1959 International Yard and Pound Agreement):
- 1 ft/s = 0.3048 m/s (exactly)
- 1 foot = 0.3048 meters (exactly)
Why ft/s Instead of mph?
Time scale appropriateness: Many technical applications involve sub-second events:
- Ballistics: Bullet flight time measured in milliseconds (0.001 seconds)
- Reaction distance: Driver reaction (1-2 seconds) × speed in ft/s = distance in feet
- Hydraulics: Flow velocities through pipes/channels measured continuously, not per hour
Intuitive scale for small objects:
- "Arrow travels 300 ft/s" vs "arrow travels 205 mph"—ft/s gives clearer sense of per-second distance
- Easier mental math: "How far does projectile travel in 0.1 seconds?" → 30 feet (at 300 ft/s)
Engineering calculations: US hydraulic formulas (Manning's, Darcy-Weisbach) use ft/s natively
Standard Conversions
Imperial/US conversions:
- 1 ft/s = 0.681818 mph (or 15/22 mph exactly)
- 1 ft/s = 3,600 feet/hour
- 1 ft/s = 720 feet/minute
Key conversion (memorize):
- 60 mph = 88 ft/s (exactly: 60 × 5,280 ÷ 3,600 = 88)
- 1 mph = 1.46667 ft/s (or 22/15 exactly)
Metric conversions:
- 1 ft/s = 0.3048 m/s (exactly)
- 1 ft/s = 1.09728 km/h
- 1 ft/s = 30.48 cm/s
Marine/aviation:
- 1 ft/s = 0.592484 knots
- 1 ft/s = 0.000888 Mach (at sea level, 68°F)
Relationship to Acceleration
Feet per second squared (ft/s²) measures acceleration:
- Gravity: g = 32.174 ft/s² (standard gravity, often rounded to 32.2 ft/s²)
- Car acceleration: 0-60 mph in 5 seconds = 88 ft/s ÷ 5 = 17.6 ft/s² average
- Comparison: SI gravity = 9.80665 m/s²
Note: The Kilometer per hour is part of the metric (SI) system, primarily used globally in science and trade. The Foot per second belongs to the imperial/US customary system.
History of the Kilometer per hour and Foot per second
Kilometers per hour became a common unit of speed with the widespread adoption of the metric system for distance (kilometer) and the standard use of hours for time measurement, particularly following the advent of automobiles and trains where measuring such speeds became practical and necessary.
The Railway Origins (1840s-1860s)
European railways drive initial adoption:
The kilometer per hour emerged naturally from European railway expansion in the mid-1800s:
1840s France: The French railway network, expanding rapidly after the opening of the Paris-Rouen line in 1843, used km/h for all timetable planning. Railway engineers found that:
- Distance calculations were straightforward: 100 km at 50 km/h = 2 hours
- Hourly speeds aligned perfectly with clock-based scheduling
- Metric integration simplified track maintenance and construction measurements
1850s-1860s Central Europe: Germany, Belgium, Austria-Hungary, and Italy adopted km/h as their railway systems developed, creating a cohesive Central European railway network with standardized speed measurements.
Why not meters per second? While m/s is the SI base unit, railway engineers found it impractical:
- 27.8 m/s is harder to visualize than 100 km/h
- Hourly distances matched operational planning horizons
- Passengers understood "kilometers per hour" intuitively
The Automobile Revolution (1900s-1920s)
Cars cement km/h as the dominant standard:
1900-1910: European automobile manufacturers (Peugeot, Renault, Daimler, Benz) designed speedometers calibrated exclusively in km/h. By 1910, virtually all cars sold in continental Europe displayed km/h.
Contrasting British approach: British and American manufacturers used mph, creating a lasting divide that persists today.
1920s standardization: As road construction accelerated, European governments posted speed limits in km/h:
- France: 30 km/h in cities (1922)
- Germany: Various limits by region (Autobahn sections later unrestricted)
- Switzerland: 40 km/h urban limit (1925)
Global Metrication Wave (1960s-1980s)
The world switches from mph to km/h:
1951: Japan became the first major non-European nation to adopt km/h comprehensively for all road transport.
1974: Australia converted from mph to km/h on July 1, 1974 (metric changeover day). All speed limit signs were changed overnight, and speedometers were replaced or modified over the following years.
1977: Canada completed metrication, switching road signs from mph to km/h. The conversion created temporary confusion near the US border, where speeds suddenly appeared numerically higher (60 mph became 100 km/h).
1977: India switched to km/h as part of broader metrication efforts.
1980s: Most remaining countries completed conversion to km/h, with notable exceptions:
- United States: Retained mph despite brief 1970s metric push
- United Kingdom: Officially retained mph for roads, though rail increasingly uses km/h
- Myanmar (Burma): Uses mph but is considering metrication
Modern Global Standard (2000s-Present)
Today's landscape:
195+ countries use km/h as their legal road speed standard, representing approximately 95% of the global population.
Only 3 mph holdouts:
- United States (population: 330+ million)
- United Kingdom (population: 67+ million)
- Myanmar (population: 54+ million)
Notable exception—UK railways: British rail networks increasingly use km/h for high-speed lines (HS1 Channel Tunnel Rail Link operates in km/h), though track mile markers remain.
and Evolution
Ancient Feet to Modern Standardization
The foot through history:
- Ancient civilizations: Egyptian, Greek, Roman feet varied (285-335 mm)
- Roman pes: ~296 mm (11.65 inches)—basis for many European feet
- Medieval England: Multiple feet existed regionally (London foot, York foot)
- 1588: Queen Elizabeth I attempted standardization
- 1824: British Imperial system defined foot as 1/3 yard
- 1959: International Yard and Pound Agreement defined 1 foot = 0.3048 meters exactly
The second:
- Originally: 1/86,400 of mean solar day (Earth's rotation)
- 1967: Redefined using cesium-133 atomic transition (9,192,631,770 cycles = 1 second)
- Modern definition independent of Earth's rotation (which varies slightly)
The Foot-Pound-Second (FPS) System
British engineering standard (1800s-1960s):
- Length: foot (ft)
- Mass: pound (lb)
- Time: second (s)
- Force: poundal (1 lb·ft/s²) or pound-force (lbf)
- Energy: foot-poundal or foot-pound-force (ft·lbf)
- Velocity: feet per second (ft/s)
FPS system applications:
- Railway engineering: Train speeds, braking distances
- Ballistics: Muzzle velocity, projectile range calculations
- Hydraulics: Water flow in pipes, channels, rivers
- Structural engineering: Wind loads, beam deflections
Decline and persistence:
- 1960: SI system established internationally
- 1970s-1980s: Most countries transitioned to metric
- US holdout: American industry, construction, and firearms sectors retained FPS
- Current: US ballistics universally uses ft/s; engineering mixed (metric in automotive/aerospace, imperial in civil/construction)
Ballistics and the ft/s Standard
Why ballistics uses ft/s:
- Historical momentum: 19th-century firearms development used FPS system
- Industry standardization: Millions of existing specifications in ft/s
- Practical scale: 1,000-3,000 ft/s range fits projectile velocities well
- Reloading data: Powder charge tables, pressure curves all in imperial units
Ammunition velocity standards (all in ft/s):
- .22 LR: 1,200-1,700 ft/s
- 9mm Luger: 1,100-1,300 ft/s
- .45 ACP: 800-900 ft/s
- .223 Remington / 5.56 NATO: 3,000-3,300 ft/s
- .308 Winchester / 7.62 NATO: 2,600-2,800 ft/s
- .50 BMG: 2,800-3,000 ft/s
Chronograph measurements: All ballistic chronographs (devices measuring projectile speed) display in ft/s in US market.
US Hydraulic Engineering
Manning's Equation (open channel flow): v = (1.49/n) × R^(2/3) × S^(1/2)
Where:
- v = velocity in ft/s
- n = Manning's roughness coefficient
- R = hydraulic radius in feet
- S = channel slope (dimensionless)
Note: The 1.49 coefficient is specific to ft/s (metric version uses 1.0 with m/s)
US civil engineering applications:
- Storm drainage design
- Sanitary sewer sizing
- Irrigation canal design
- River and stream analysis
- Flood control structures
Persistence reason: US infrastructure built over 150+ years using imperial units—retrofitting millions of engineering drawings impractical.
Driver Education and Safety
The "60 mph = 88 ft/s" Rule:
Used universally in US driver education to teach reaction distance:
Reaction time (typical): 1.5 seconds Distance traveled (at 60 mph): 1.5 × 88 = 132 feet before braking begins
Stopping distance breakdown (60 mph on dry pavement):
- Reaction distance: 132 feet (time to perceive, react, move foot to brake)
- Braking distance: ~180 feet (actual braking to stop)
- Total stopping distance: ~312 feet (longer than a football field!)
Why ft/s is better than mph for this:
- Intuitive: "I travel 88 feet every second at highway speed"
- Easy calculation: seconds × ft/s = feet
- Using mph requires: mph × 1.467 × seconds = feet (harder mental math)
Common Uses and Applications: kilometers per hour vs feet per second
Explore the typical applications for both Kilometer per hour (metric) and Foot per second (imperial/US) to understand their common contexts.
Common Uses for kilometers per hour
Road Traffic Worldwide
The most common unit for speed limits and vehicle speeds (speedometers) worldwide, except in countries like the US and UK.
Global speedometer standard:
- 195+ countries require speedometers calibrated in km/h
- Dual displays common in mph-primary countries (UK cars show both mph and km/h)
- Import vehicles often need speedometer conversion or overlay decals
Speed enforcement:
- Fixed speed cameras display limits in km/h globally
- Radar guns used by police calibrated in km/h in metric countries
- GPS navigation systems default to km/h in most regions (user-changeable)
Driver education:
- Driving schools in km/h countries teach speed estimation in km/h
- Stopping distances calculated using km/h (e.g., "at 100 km/h, stopping distance is approximately 100 meters on dry pavement")
Meteorology and Weather Reports
Often used in public weather forecasts to report wind speeds, especially in metric countries.
Daily weather forecasts:
- TV and radio: "Winds gusting up to 60 km/h expected this afternoon"
- Weather apps: Display wind speed in km/h by default in most countries
- Weather warnings: "Wind advisory in effect for sustained winds of 50-70 km/h"
Severe weather:
- Tropical cyclone tracking: "System intensifying to 180 km/h sustained winds"
- Tornado warnings: While some regions use mph, many use km/h for consistency
- Storm surge modeling: Wind speeds in km/h used for prediction models
Aviation weather (METAR reports):
- Actually use knots (nautical miles per hour) as the international standard, but public-facing forecasts convert to km/h for general audiences
Navigation and Maritime Use
Used alongside other units like knots in some aviation and maritime contexts, although less common than knots for primary navigation.
Maritime context:
- Recreational boating: Many countries display boat speeds in km/h on consumer GPS units
- Ship traffic services: Professional shipping uses knots, but coastal authorities may communicate speeds to recreational vessels in km/h
- Current speeds: Ocean and river current speeds sometimes expressed in km/h for public understanding
Aviation (limited use):
- General aviation: Some small aircraft in Europe display airspeed in km/h
- Groundspeed: GPS navigation sometimes shows groundspeed in km/h for pilots' situational awareness
- Professional aviation: Knots remain the global standard for airspeed and navigation
Sports and Athletics
Sometimes used to describe speeds in cycling, skiing, or running over longer distances.
Cycling:
- Professional race coverage: "The peloton is maintaining 45 km/h on the flat sections"
- Bike computers: Display current speed, average speed, and maximum speed in km/h
- Training metrics: Cyclists track average speeds to gauge fitness improvements
Running:
- Treadmill displays: Often show speed in km/h (especially in metric countries)
- GPS running watches: Can display pace as min/km or speed as km/h
- Race commentary: "The lead pack is running at approximately 21 km/h pace"
Skiing and snowboarding:
- Speed skiing competitions: Measured in km/h (world record: 254.958 km/h, 2016)
- Ski resort speed checks: Display current speed in km/h at base of runs
- Avalanche speeds: "Avalanches can reach 130 km/h in steep terrain"
Other sports:
- Tennis serve speeds: Displayed in km/h globally (fastest recorded: 263 km/h by Sam Groth, 2012)
- Baseball pitch speeds: In metric countries, displayed as km/h (~150 km/h for fast pitches)
- Golf ball speed: Club head and ball speeds measured in km/h in some markets
Scientific and Engineering Applications
Used in physics education, engineering calculations, and scientific research where metric units are standard:
Physics education:
- Introductory kinematics: "A car accelerates from 0 to 100 km/h in 8 seconds—calculate acceleration"
- Energy calculations: Kinetic energy problems often use km/h, then convert to m/s for SI calculations
- Momentum problems: "Two vehicles collide—one traveling at 60 km/h, the other at 80 km/h"
Wind engineering:
- Building design: Wind load calculations use km/h for reference wind speeds
- Bridge engineering: Suspension bridges designed to withstand winds of 150+ km/h
Transportation planning:
- Traffic flow modeling: Simulations use km/h for vehicle speeds
- Capacity analysis: "This highway section can accommodate 2,000 vehicles per hour at 100 km/h"
- Emission modeling: Fuel consumption and emissions vary significantly by speed (optimal efficiency typically 80-90 km/h for modern cars)
Climate science:
- Atmospheric circulation: Jet stream speeds measured in km/h
- Hurricane research: Storm tracking and intensity analysis
Consumer Products and Specifications
Speed ratings and specifications:
Tires:
- Speed ratings: European tire speed codes (e.g., "H-rated: 210 km/h maximum")
- Winter tire testing: Performance ratings at various speeds in km/h
Electric scooters and e-bikes:
- Maximum speed limits: Regulations often specify "limited to 25 km/h" (common EU e-bike limit)
- Product specifications: "Top speed: 30 km/h" on consumer packaging
Drones:
- Maximum flight speed: "Can reach 68 km/h in Sport Mode"
- Return-to-home speed: Typically 30-50 km/h for consumer drones
Recreational vehicles:
- Golf carts: Typically 20-25 km/h maximum
- ATVs and UTVs: Specified in km/h in metric markets
When to Use feet per second
Across Industries
Ballistics and Firearms
- Ammunition specifications: All US ammo rated in ft/s muzzle velocity
- Chronograph testing: Velocity measurement devices display ft/s
- Ballistic calculators: Trajectory prediction software requires ft/s input
- Reloading data: Powder charge tables show expected ft/s velocities
Archery and Hunting
- Bow performance: IBO (International Bowhunting Organization) speed ratings in ft/s
- Arrow selection: Spine charts factor in bow speed (ft/s)
- Kinetic energy calculations: KE = (arrow weight × velocity²) ÷ 450,240 (weight in grains, velocity in ft/s → energy in foot-pounds)
US Civil Engineering
- Open channel flow: Manning's equation uses ft/s for rivers, canals, drainage
- Storm water management: Inlet design, detention pond sizing
- Sanitary sewer design: Minimum 2 ft/s to prevent settling
- Flood analysis: Peak flow velocities in ft/s
Driver Education and Safety
- Reaction distance teaching: "At 60 mph, you travel 88 feet every second"
- Following distance: "3-second rule" = 3 × 88 = 264 feet at 60 mph
- Crash reconstruction: Skid mark analysis uses ft/s for velocity calculations
Sports Science
- Baseball/softball: Pitch speed tracking (radar guns display ft/s or mph)
- Golf: Launch monitors measure clubhead and ball speed in ft/s
- Track and field: Sprint speeds converted to ft/s for analysis
Aviation (Limited Use)
- Rate of climb/descent: Feet per minute (fpm), but convertible to ft/s
- Ground speed calculations: Sometimes expressed in ft/s for short-field operations
- Note: Aviation primarily uses knots (nautical miles per hour)
Additional Unit Information
About Kilometer per hour (km/h)
Where is km/h primarily used?
Kilometers per hour is the standard unit for road speed in most countries around the world that use the metric system—195+ countries representing approximately 95% of the global population. This includes all of Europe (except UK for roads), Asia (except Myanmar), South America, Africa, Australia, and Canada. Only the United States, United Kingdom (for road traffic), and Myanmar primarily use miles per hour (mph) instead.
Is km/h an SI unit?
While it uses SI units (kilometer and hour derived from second), the official SI unit for speed is meters per second (m/s). However, km/h is accepted for use with SI and is the standard for practical applications like road speed limits and weather reports. Scientists typically convert km/h to m/s for calculations (1 km/h = 0.278 m/s), but km/h remains universally understood and used globally for everyday speed measurements.
How do you convert km/h to mph?
To convert kilometers per hour to miles per hour, divide by 1.609 (or multiply by 0.621371 for more precision). Quick approximation: divide by 1.6. For example:
- 100 km/h ÷ 1.6 ≈ 62.5 mph (actual: 62.14 mph)
- 80 km/h ÷ 1.6 = 50 mph
- 120 km/h ÷ 1.6 = 75 mph
For a rougher estimate, multiply km/h by 0.6: 100 km/h × 0.6 = 60 mph (close enough for casual conversation).
How do you convert km/h to m/s?
Divide the speed in km/h by 3.6 to get meters per second. Formula: m/s = km/h ÷ 3.6. For example:
- 100 km/h ÷ 3.6 = 27.78 m/s
- 90 km/h ÷ 3.6 = 25 m/s
- 36 km/h ÷ 3.6 = 10 m/s
Why 3.6? Because 1 km = 1,000 meters and 1 hour = 3,600 seconds, so 1,000 ÷ 3,600 = 1 ÷ 3.6. To convert back from m/s to km/h, multiply by 3.6.
What is a good walking speed in km/h?
A typical comfortable walking speed is 5 km/h (about 3.1 mph), which translates to covering 1 kilometer in 12 minutes. Speeds vary by activity:
- Leisurely stroll: 3-4 km/h (window shopping, elderly pace)
- Average walk: 5 km/h (standard comfortable pace)
- Brisk walk: 6-7 km/h (fitness walking, power walking)
- Speed walking (race walking): 10-15 km/h (Olympic athletes reach 13-15 km/h)
For reference, pedestrian crossing signals are typically designed assuming 4-5 km/h walking speed.
What is the typical highway speed in km/h?
Highway speed limits vary significantly by country, but 100-130 km/h (62-81 mph) is the most common range globally:
- 100 km/h: Canada, Australia, Japan (many highways)
- 110-120 km/h: Spain (120), Italy (130), France (130), Australia (110)
- 130 km/h: France, Austria, Belgium, Italy (motorways)
- 140 km/h: Poland, Bulgaria (motorway limits)
- Unlimited sections: Germany (Autobahn—advised 130 km/h, many sections unrestricted)
Most drivers maintain 100-110 km/h as a comfortable highway cruising speed.
How fast is 100 km/h?
100 km/h is a common highway speed globally, equal to:
- 62.1 mph (about the speed limit on many US interstates)
- 27.8 meters per second (traveling the length of a basketball court every second)
- 1.67 kilometers per minute (1 km every 36 seconds)
Reference points:
- 100 km/h = 100 meters traveled every 3.6 seconds
- At this speed, your reaction distance (before braking) is about 28 meters
- Total stopping distance on dry pavement: approximately 100 meters
- A commercial jet's cruising speed is about 9× faster (900 km/h)
What speed is considered fast for a car?
"Fast" depends on context, but general guidelines:
On public roads:
- 80-100 km/h: Moderate highway cruising
- 120-140 km/h: Fast highway driving (legal limits in some European countries)
- 160+ km/h: Very fast (exceeds most legal limits worldwide, except unrestricted Autobahn)
Vehicle performance:
- 200 km/h (124 mph): Sports car territory
- 250 km/h (155 mph): High-performance sports cars (often electronically limited)
- 300+ km/h (186+ mph): Supercars (Lamborghini, Ferrari, McLaren)
- 400+ km/h (250+ mph): Hypercars (Bugatti Chiron top speed: 490 km/h / 304 mph)
For everyday driving, anything over 140 km/h is considered "fast" in most contexts.
Do planes use km/h or mph?
Professional aviation uses knots (nautical miles per hour) as the international standard for airspeed and navigation, not km/h or mph. However, speeds are often converted to km/h or mph for public understanding:
Aviation standards:
- Airspeed, wind speed, groundspeed: Measured in knots
- Altitude: Measured in feet (even in metric countries)
- Distance: Measured in nautical miles
For reference:
- 1 knot = 1.852 km/h (exactly)
- Typical commercial jet cruise: 450-480 knots = 830-890 km/h
- Fast business jet: 500+ knots = 925+ km/h
Some small general aviation aircraft in Europe display airspeed in km/h, but this is uncommon professionally.
Why doesn't the whole world use km/h?
95% of the world does use km/h—only three countries primarily use mph: the United States, United Kingdom (roads only), and Myanmar. The reasons these countries retain mph include:
United States:
- Infrastructure cost: Replacing millions of road signs would cost billions
- Cultural resistance: Strong attachment to traditional units ("metric conversion" politically unpopular)
- Dual system: US already uses metric extensively in science, medicine, military, but not road transport
United Kingdom:
- Partial metrication: UK uses metric for most things (fuel sold in liters, food in grams) but retained mph for roads and distances
- Historical preservation: Miles deeply embedded in British culture and infrastructure
- Compromise approach: Speed limits in mph, but fuel economy measured in L/100 km creates confusion
Myanmar:
- Considering metrication: Government has discussed switching to metric system including km/h
- Limited road infrastructure: Smaller road network makes conversion more feasible
Historical note: Canada, Australia, and most former British colonies successfully converted from mph to km/h in the 1970s-1980s, proving large-scale conversion is achievable with political will.
How accurate are car speedometers in km/h?
Car speedometers are legally required to overestimate speed slightly to prevent drivers from accidentally speeding. Regulations vary by country:
European Union (UN ECE R39 regulation):
- Speedometer must never underestimate speed
- Can overestimate by up to 10% + 4 km/h
- Example: True speed 100 km/h → speedometer shows 100-114 km/h (allowed range)
Australia (ADR 18):
- Similar to EU: Never under-read, can over-read up to 10% + 4 km/h
Typical real-world accuracy:
- Most modern cars: Overestimate by 2-5% at highway speeds
- 100 km/h indicated = 95-98 km/h actual speed (common)
- GPS speedometers: Generally more accurate (±1 km/h), but can lag during acceleration
Why overestimate? Manufacturers err on the side of caution to avoid liability if speedometer under-reads and drivers get speeding tickets or cause accidents.
About Foot per second (ft/s)
Is ft/s faster than mph?
No—ft/s is a smaller unit, so the number is bigger for the same speed.
- 1 mph = 1.467 ft/s
- 100 ft/s = 68 mph (the ft/s number is bigger, but it's actually slower than "100 mph")
Think of it like inches vs feet: 12 inches = 1 foot. "12" is bigger than "1", but they're the same length. Similarly, "100 ft/s" looks bigger than "68 mph", but they're the same speed.
What is the speed of sound in ft/s?
Approximately 1,125 ft/s at sea level, 68°F (767 mph, 343 m/s) = Mach 1
Temperature dependence:
- 32°F (0°C): 1,087 ft/s
- 68°F (20°C): 1,125 ft/s (standard reference)
- 86°F (30°C): 1,145 ft/s
Practical rule: "Sound travels about 1,100 feet per second"
Lightning distance trick:
- See lightning flash
- Count seconds until thunder: "one Mississippi, two Mississippi, three..."
- Multiply seconds by 1,100 feet
- Divide by 5,280 (feet per mile) to get miles
- Example: 5 seconds → 5,500 feet → ~1 mile away
Why bullets are "supersonic" or "subsonic":
- Supersonic (> 1,125 ft/s): Creates sonic boom/crack
- Subsonic (< 1,125 ft/s): No sonic crack (quieter with suppressor)
How do I convert mph to ft/s in my head?
Method 1 (rough): Multiply by 1.5
- 60 mph × 1.5 = 90 ft/s (actual: 88, close!)
- 40 mph × 1.5 = 60 ft/s (actual: 58.7, pretty close)
Method 2 (better): Use the "22/15 rule" or remember key values
- 30 mph = 44 ft/s
- 60 mph = 88 ft/s
- 90 mph = 132 ft/s
- Scale from these: 45 mph = halfway between 30 and 60 → (44+88)/2 = 66 ft/s
Method 3 (precise): Multiply by 1.467 (or 22/15)
- 50 mph × 1.467 = 73.35 ft/s
Why do bullets use ft/s instead of mph?
Four main reasons:
- Historical: US firearms industry developed using FPS system (foot-pound-second)
- Practical scale: Bullet velocities (1,000-3,000 ft/s) fit well, whereas 700-2,000 mph sounds awkward
- Short-duration events: Bullets travel for fractions of a second, so "per second" is more intuitive than "per hour"
- Ballistic calculations: Easier math for drop (inches), time of flight (milliseconds), energy (foot-pounds) when velocity is in ft/s
Example: .223 Rem bullet at 3,200 ft/s
- Distance in 0.1 seconds: 320 feet (easy mental math)
- If stated as 2,182 mph: distance in 0.1 sec requires mph × 1.467 × 0.1 = 320 feet (harder)
What is terminal velocity in ft/s?
Human skydiver:
- Belly-to-earth (stable, arms/legs spread): 176 ft/s (120 mph, 54 m/s)
- Head-down streamline (diving position): 295 ft/s (200 mph, 90 m/s)
- With parachute deployed: 15-25 ft/s (10-17 mph)—safe landing speed
Other objects:
- Raindrop (small, 1mm): 20 ft/s
- Raindrop (large, 5mm): 30 ft/s
- Baseball: 146 ft/s (100 mph)
- Penny (myth-busting): 30-50 ft/s (not lethal!)
- Bowling ball: 335 ft/s (228 mph)—dangerous!
Why terminal velocity varies: Air resistance balances weight. Bigger, heavier, or more streamlined = higher terminal velocity.
How fast is 300 ft/s in mph?
300 ft/s = 204.5 mph
Formula: 300 ft/s × 0.682 = 204.5 mph
Context: This is a common archery speed (compound bow arrow) or paintball velocity limit (280-300 ft/s)
Comparison:
- 300 ft/s = subsonic (below 1,125 ft/s speed of sound)
- 300 ft/s = 91.4 m/s (metric)
- 300 ft/s = 199 knots (marine/aviation)
What does "subsonic ammo" mean?
Subsonic ammunition: Muzzle velocity < 1,125 ft/s (speed of sound)
Why use subsonic:
- No sonic crack: Supersonic bullets create a sonic boom as they break the sound barrier—sounds like a loud "crack"
- Suppressor-friendly: With a suppressor (silencer), subsonic ammo is much quieter—only the muzzle blast is heard, not the sonic crack
- Hearing protection: Even without suppressor, subsonic is less loud
Common subsonic rounds:
- .45 ACP: 850-900 ft/s (naturally subsonic, heavy bullet)
- 9mm subsonic: 950-1,050 ft/s (special loads, lighter powder charge)
- .22 LR subsonic: 1,050-1,100 ft/s
Supersonic ammunition: Velocity > 1,125 ft/s
- Standard .223 Rem: 3,200 ft/s (almost 3× speed of sound!)
- Standard 9mm: 1,200 ft/s (just barely supersonic)
How far does a car travel in 1 second at 60 mph?
88 feet (exactly)
Breakdown:
- 60 mph = 60 miles/hour
- 60 miles/hour × 5,280 feet/mile ÷ 3,600 seconds/hour = 88 feet/second
Why this matters for safety:
- Reaction time: Average driver takes 1.5 seconds to react to hazard
- Distance during reaction: 1.5 seconds × 88 ft/s = 132 feet (before even touching brake!)
- Braking distance: Additional ~180 feet to stop (dry pavement)
- Total stopping distance: 132 + 180 = 312 feet at 60 mph
Following distance "3-second rule":
- At 60 mph, maintain 3 × 88 = 264 feet behind car ahead
- Gives 2× reaction distance (safer margin)
Can I use ft/s in scientific equations?
Yes, but you must use imperial units consistently:
Kinetic energy (imperial): KE (foot-pounds) = ½ × mass (slugs) × velocity² (ft/s)²
- 1 slug = 32.174 pounds-mass
- Or: KE (ft·lbf) = weight (lbf) × velocity² (ft/s)² / (2 × 32.2)
Force (imperial): F (pound-force) = mass (slugs) × acceleration (ft/s²)
- Or: F (lbf) = (weight in lbf / 32.2) × acceleration (ft/s²)
For scientific work, SI units (m/s, kg, Newtons, Joules) are strongly preferred:
- No slugs vs pounds confusion
- International standards require SI
- Easier unit conversions (all decimal)
Bottom line: You can use ft/s in calculations, but it's more complex than metric. For ballistics and US engineering where ft/s is standard, imperial equations exist. For research/publication, convert to m/s.
What's the difference between ft/s and ft/s²?
ft/s (feet per second): Velocity—how fast you're moving ft/s² (feet per second squared): Acceleration—how quickly your velocity changes
Example (free fall):
- Gravity acceleration: g = 32.2 ft/s²
- After 0 seconds: velocity = 0 ft/s
- After 1 second: velocity = 32.2 ft/s (acceleration added 32.2 ft/s)
- After 2 seconds: velocity = 64.4 ft/s (acceleration added another 32.2 ft/s)
- After 3 seconds: velocity = 96.6 ft/s
Car example (0-60 mph in 5 seconds):
- Change in velocity: 60 mph = 88 ft/s
- Time: 5 seconds
- Average acceleration: 88 ft/s ÷ 5 seconds = 17.6 ft/s²
Conversion Table: Kilometer per hour to Foot per second
| Kilometer per hour (km/h) | Foot per second (ft/s) |
|---|---|
| 0.5 | 0.456 |
| 1 | 0.911 |
| 1.5 | 1.367 |
| 2 | 1.823 |
| 5 | 4.557 |
| 10 | 9.113 |
| 25 | 22.784 |
| 50 | 45.567 |
| 100 | 91.134 |
| 250 | 227.836 |
| 500 | 455.672 |
| 1,000 | 911.344 |
People Also Ask
How do I convert Kilometer per hour to Foot per second?
To convert Kilometer per hour to Foot per second, enter the value in Kilometer per hour in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our speed converter page to convert between other units in this category.
Learn more →What is the conversion factor from Kilometer per hour to Foot per second?
The conversion factor depends on the specific relationship between Kilometer per hour and Foot per second. 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 Foot per second back to Kilometer per hour?
Yes! You can easily convert Foot per second back to Kilometer per hour by using the swap button (⇌) in the calculator above, or by visiting our Foot per second to Kilometer per hour converter page. You can also explore other speed conversions on our category page.
Learn more →What are common uses for Kilometer per hour and Foot per second?
Kilometer per hour and Foot per second are both standard units used in speed measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our speed converter for more conversion options.
For more speed conversion questions, visit our FAQ page or explore our conversion guides.
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National Institute of Standards and Technology — Standards for speed and velocity measurements
Last verified: December 3, 2025