Convert ft/s to mph feet per second ↔ miles per hour Free Online Secure
Type a value in feet per second and read it in miles per hour at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Convert from feet per second
Convert to miles per hour
Common values — Convert ft/s to mph (feet per second ↔ miles per hour)
| ft/s | mph |
|---|---|
| 1 | 0.681818181818 |
| 2 | 1.36363636364 |
| 3 | 2.04545454545 |
| 5 | 3.40909090909 |
| 10 | 6.81818181818 |
| 20 | 13.6363636364 |
| 50 | 34.0909090909 |
| 100 | 68.1818181818 |
Where these units come from
Speed has no unit of its own: it is a length divided by a time, so every trade simply kept the length it was already using. That is why the same motion is 100 km/h on a European road sign, 62 mph on an American one and 27.8 m/s in a physics problem. The knot is the oldest of them and the most literal: sailors paid out a line with knots tied at even spacing and counted how many ran through their fingers while a sand glass emptied, so the speed was read off in knots. One knot is one nautical mile per hour, and a nautical mile is a minute of latitude — which is why ships and aircraft still use it. The speed of light is the odd one out: since 1983 it is not measured but fixed at exactly 299,792,458 m/s, because the metre is now defined from it.
Where you meet them
Kilometres and miles per hour live on speedometers and road signs, metres per second in physics, engineering and wind reports, feet per second in ballistics and in American machine shops. Knots carry shipping, aviation and marine weather, and Mach numbers appear wherever an aircraft is fast enough for the air's own stiffness to matter. The speed of light turns up less in daily life than in distances: a light year is simply how far it gets in one.
Questions people ask
Is Mach 1 a fixed speed?
No. Mach is a ratio to the speed of sound in the surrounding air, and sound travels more slowly in colder air. This page uses the standard sea-level figure, 340.294 m/s, so Mach 1 here is about 1225 km/h. At the altitude airliners cruise at, the air is some 50 degrees colder and the same Mach 1 is roughly a tenth slower. An aircraft can therefore hold a constant Mach number while its speed over the ground changes.
Why do ships and aircraft use knots rather than km/h?
Because a nautical mile is one minute of arc of latitude. A vessel making one knot covers one minute of latitude in an hour, so speed, time and position on a chart fit together without conversion. The same reasoning kept the nautical mile at exactly 1852 metres rather than rounding it to something tidier.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
Feet per second in miles per hour: racehorses, birds, lifts and waves
Textbook problems, engineering notes and sports-science papers in the United States often give speed in feet per second, while the news, the road and the stadium scoreboard all use miles per hour. A racehorse covers 64.5 ft/s, which sounds abstract; the same horse at 44 mph is something people can picture. To convert ft/s to mph, multiply by 0.6818, which is exactly 15/22: 88 ft/s is 60 mph, 100 ft/s is 68.2 mph and 176 ft/s is 120 mph. The calculator above multiplies as you type, and the sections below show what these numbers look like for animals, machines and weather.
The page gives the rule with worked examples, a profile of each unit, a comparison and a long series of everyday cases, followed by common mistakes. The calculation runs in your browser and nothing you type is sent anywhere. For official records or safety limits, consult the source.
How to convert ft/s to mph: multiply by 0.6818
The rule
A mile is 5,280 feet and an hour is 3,600 seconds, so one foot per second equals 3,600 / 5,280 = 0.681818 mph, exactly 15/22. To convert ft/s to mph, multiply the ft/s figure by 0.6818. That gives 22 ft/s as 15 mph, 66 ft/s as 45 mph and 300 ft/s as 204.5 mph. To go back, multiply mph by 1.4667.
Worked examples
A person walking at 4.4 ft/s is moving at 3 mph. A car at 88 ft/s is doing 60 mph. A roller-coaster train at 187.7 ft/s reaches 128 mph, and sound, at 1,125 ft/s, travels at 767 mph.
Why the factor is exact
The statute mile is defined as 5,280 feet and the hour as 3,600 seconds, so the ratio 15/22 is an exact fraction. Rounding only appears when you write the answer as a decimal.
A quick sanity test
The figure in mph is almost a third smaller than the figure in ft/s. If a “convert ft/s to mph” calculation gave a larger number than you started with, the factor was used in the wrong direction.
The foot per second
The unit of formulas
The foot per second is the speed unit of the US customary system when length is in feet and time in seconds. You meet it in textbook formulas for falling bodies, in engineering calculations and in many scientific papers from American laboratories.
Where it appears
Textbooks, laboratory reports, engineering tables and simulation code.
The mile per hour
The unit of the road and the scoreboard
The mile per hour is the speed of everyday life in the United States and the United Kingdom. Speed limits, car speedometers, sports broadcasts and weather bulletins all use it.
Where it appears
Road signs, broadcasts, weather reports and car brochures.
Feet per second against miles per hour
One ft/s is 0.682 mph, so the number in mph is almost a third smaller. A speed of 100 ft/s is 68.2 mph and one of 200 ft/s is 136.4 mph. Both are American units, but they serve different purposes: ft/s for calculation, mph for communication.
The conversion is exact and hides no rounding. The main trap is direction: from ft/s to mph the figure falls.
Where the conversion shows up
Animals
A cheetah sprints at about 100 ft/s, 68 mph. A racehorse reaches 64.5 ft/s, 44 mph, and a greyhound 58.7 ft/s, 40 mph. A peregrine falcon in a dive passes 300 ft/s, 204 mph. A “convert ft/s to mph” calculation puts the animals on the scale of a motorway.
Machines and buildings
A fast lift moves at 67 ft/s, 46 mph, and a normal escalator at 1.5 ft/s, 1 mph. Engineers design the cables, brakes and comfort limits in ft/s, while brochures talk of mph or metres per second.
Waves and weather
An ocean swell with a period of 10 seconds travels at 51 ft/s, 35 mph. A tsunami in deep water races at 647 ft/s, 441 mph, as fast as a jet airliner. Wind gusts of 88 ft/s are 60 mph.
Horse racing
A furlong is 660 feet. A horse at 55 ft/s, 37.5 mph, runs it in 12 seconds. The Kentucky Derby is a mile and a quarter, 6,600 feet; Secretariat's record time of 1:59.4 works out to 55.3 ft/s, or 37.7 mph, held for the whole distance. Short sprints are faster, up to 44 mph over a quarter mile.
Rounding and precision
On a poster, round to whole mph: 187.7 ft/s is 128 mph. For a force calculation, keep the decimals, since the speed will be squared. An error of 1 mph is 1.47 ft/s, and it shifts the energy at 128 mph by about 1.6 per cent.
Landmarks to memorise
22 ft/s is 15 mph. 44 ft/s is 30 mph. 66 ft/s is 45 mph. 88 ft/s is 60 mph. 110 ft/s is 75 mph. 132 ft/s is 90 mph. To convert ft/s to mph by eye, start from the fact that 88 ft/s is 60 mph and scale from there.
Reference ladder
1 ft/s is 0.68 mph. 5 ft/s is 3.41 mph. 10 ft/s is 6.82 mph. 30 ft/s is 20.45 mph. 50 ft/s is 34.09 mph. 120 ft/s is 81.82 mph. 200 ft/s is 136.36 mph. 500 ft/s is 340.91 mph. A table like this makes checks quick.
Checking by reversing
To check a “convert ft/s to mph” calculation result, multiply the answer by 1.4667. If 88 ft/s became 60 mph, then 60 times 1.4667 returns 88. A second test is size: the number of mph should be about two thirds of the number of ft/s.
Link to km/h
One ft/s is 1.097 km/h and one mph is 1.609 km/h. So 88 ft/s is 96.6 km/h and 60 mph. For a reader outside America, the km/h column is usually the one that means something.
A worked example
A coaster reaches 205 ft/s at the end of its launch. The speed is 205 × 0.6818 = 139.8 mph, or 225 km/h. If the launch takes 4 seconds, the mean acceleration is 51.3 ft/s², which is 1.59 g. One calculation gives the speed in mph for the poster and the acceleration in g for the safety file.
Sound and supersonic flight
Sound travels at 1,125 ft/s, 767 mph, at 20 degrees Celsius. A supersonic jet at 2,000 ft/s moves at 1,364 mph, about Mach 1.8. Mach 1 at sea level is 761 mph. Older aerodynamics texts quote ft/s, popular articles quote mph.
Balls in sport
A baseball pitched at 146.7 ft/s is travelling at 100 mph, and reaches the plate in 0.41 seconds. A golf ball launched at 250 ft/s is at 170 mph. Television broadcasts in the US show mph, while papers on ball flight use ft/s.
Ski lifts
A high-speed chairlift moves at 15 to 20 ft/s, 10 to 13.6 mph, and a surface lift at 6 to 10 ft/s, 4 to 7 mph. Resorts quote mph, but the engineers who calculate braking and capacity work in feet per second.
Gusts
A gust of 88 ft/s is 60 mph. A mean wind of 44 ft/s, 30 mph, with gusts to 66 ft/s, 45 mph, means unsteady air. Poorly fastened roofs fail because of the gusts, not the mean.
Birds
A common swift flies level at about 101 ft/s, 69 mph, a hummingbird at 44 ft/s, 30 mph, and a peregrine in a stoop at up to 355 ft/s, 242 mph. A golden eagle dives at around 220 ft/s, 150 mph. Bird speeds are quoted in mph by naturalists and in m/s by researchers.
Wind pressure
The dynamic pressure at 88 ft/s, 60 mph, is 0.00119 × 88² / 2 = 4.6 lbf/ft², about 220 Pa. Doubling the wind speed quadruples the pressure: at 176 ft/s, 120 mph, it is 18.4 lbf/ft². US building codes give design wind speeds in mph.
Rivers and rafting
A fast river flows at 10 ft/s, 6.8 mph. A touring kayak makes 5 ft/s, 3.4 mph. Against a 6 ft/s current, 4.1 mph, the kayak barely holds its place. Rafting guides in the United States quote water speed in ft/s and mph.
Hurricanes by category
Category 1 starts at 74 mph, 108.5 ft/s. Category 2 at 96 mph, 140.8 ft/s. Category 3 at 111 mph, 162.8 ft/s. Category 4 at 130 mph, 190.7 ft/s, and category 5 at 157 mph, 230.3 ft/s. Forecast centres quote mph and knots, while research papers use ft/s and m/s.
Land speed records
The absolute land speed record of 763 mph is 1,119 ft/s and passes the speed of sound. A top-fuel dragster reaches 330 mph, 484 ft/s, and covers 1,000 feet in under four seconds. These numbers show how much power the engines produce.
Knowing which unit you have
If you see 88 next to a chronograph, it is probably ft/s, and if you see 60 beside a motorway, it is probably mph. The two differ by almost 47 per cent, so write the unit beside the number. A good report says "88 ft/s (60 mph)".
Water parks
A water slide delivers a rider at 25 to 35 ft/s, 17 to 24 mph. A vertical drop slide can reach 40 ft/s, 27 mph. Parks advertise in mph, while designers calculate in ft/s.
Trains and trams
An American passenger train at 79 mph moves at 116 ft/s. A city tram at 25 mph moves at 36.7 ft/s. At a level crossing, a barrier that is down for 20 seconds corresponds to a train 2,320 feet, about 0.44 miles, away.
Sports photography
A photographer following a cyclist at 30 mph, 44 ft/s, needs a shutter of at least 1/500 second to freeze the action. In that time the bike advances 0.088 feet, 2.7 centimetres.
Light aircraft
A light aircraft at 100 mph flies at 146.7 ft/s. The usual lift-off speed of 60 mph is 88 ft/s. The pilot reads mph or knots, while the performance chart may list ground roll in feet and speeds in ft/s.
Game engines
Physics engines in video games sometimes store speeds in ft/s while the interface shows mph. A vehicle with 220 ft/s in code appears as 150 mph on screen. If you adapt a game, check which unit the constants use.
Lifts in tall buildings
The fastest lifts in the world run at about 67 ft/s, which is 20.5 m/s and 46 mph. A mid-rise lift at 6 ft/s, 4.1 mph, takes about 30 seconds to climb 180 feet. Designers limit acceleration to roughly 0.1 g to spare passengers' ears and stomachs.
Impact and drop height
An impact at 44 ft/s, 30 mph, has the energy of a fall from 30 feet, 9.1 metres. At 88 ft/s, 60 mph, the equivalent is 120 feet, nearly 37 metres. Because energy follows the square of the speed, doubling the speed quadruples the consequences.
A falling stone
A stone dropped for 3 seconds reaches 96.5 ft/s, 65.8 mph. After 5 seconds it reaches 160.9 ft/s, 109.7 mph, ignoring drag. With air resistance the speed would be lower, which is why a feather falls slower than a hammer on Earth.
Cycling
A road peloton rolls along at 25 mph, 36.7 ft/s, and a sprinter at the finish reaches 45 mph, 66 ft/s. The hour record on the track is about 34.5 mph, 50.6 ft/s. Cyclists' computers show mph or km/h, while wind-tunnel reports for the same riders use ft/s or m/s, so a “convert ft/s to mph” calculation bridges the two.
Swimming
An Olympic 100 metre freestyle in 46.4 seconds means an average of 2.155 m/s, 7.07 ft/s, which is only 4.8 mph. Water is so much denser than air that even the best swimmers are slow by land standards. Coaches in the US sometimes log pace in ft/s when they study stroke mechanics, and to convert ft/s to mph on such data is a routine step.
Ventilation ducts
A duct carrying air at 1,000 feet per minute moves it at 16.7 ft/s, which is 11.4 mph. American catalogues use ft/min, designers' formulas ft/s, and the public mph. Dividing by 60 turns ft/min into ft/s, and then a “convert ft/s to mph” calculation gives the figure people understand.
The speed of the planet
A point on the equator turns with the Earth at about 1,526 ft/s, 1,040 mph. The planet moves around the Sun at 97,700 ft/s, roughly 66,600 mph. Astronomers use km/s, but old American texts give ft/s, and a “convert ft/s to mph” calculation makes such figures comparable with an aeroplane or a bullet.
Escalators and moving walkways
An escalator moves at 1.5 ft/s, 1 mph. A moving walkway in an airport is 2.5 ft/s, 1.7 mph. A walker on top of the walkway adds 4.4 ft/s, 3 mph, and travels at 6.9 ft/s, 4.7 mph, relative to the ground. Safety codes set an upper limit for these speeds.
Treadmills and training
A treadmill at 6 mph is moving at 8.8 ft/s. A ten-minute mile is 6 mph, and a seven-minute mile is 8.6 mph, 12.6 ft/s. Fitness equipment sold in the United States uses mph, but exercise-physiology papers quote m/s or ft/s.
Ocean waves
The speed of a deep-water wave in feet per second is about 5.12 times its period in seconds. A 6-second wave moves at 30.7 ft/s, 21 mph. A 12-second swell moves at 61.4 ft/s, 41.9 mph. Surfers and mariners speak in mph or knots, while oceanographers use ft/s or m/s.
Tsunamis
A tsunami in 13,000 feet of water travels at the square root of g times depth, 647 ft/s, which is 441 mph. As it enters shallower water it slows to 100 ft/s, 68 mph, while the wave grows in height. The numbers explain why coastal warnings must be issued within minutes.
The mental shortcut
To convert ft/s to mph in your head, multiply by 2, divide by 3 and add 2 per cent. For 88 ft/s: 176 divided by 3 is 58.7, plus 2 per cent is 59.8, close to 60. For 150 ft/s: 100 plus 2 per cent is 102 mph, against the exact 102.3.
Spreadsheet formulas
To convert ft/s to mph in a spreadsheet, put the ft/s figures in column A and type =A2*15/22 in column B. For the reverse, use =B2*22/15. The fraction avoids rounding altogether and works in every spreadsheet program.
More values for convert ft/s to mph
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 ft/s = 0.0681818 mph
- 0.5 ft/s = 0.340909 mph
- 3 ft/s = 2.04545 mph
- 4 ft/s = 2.72727 mph
- 7 ft/s = 4.77273 mph
- 15 ft/s = 10.2273 mph
- 20 ft/s = 13.6364 mph
- 75 ft/s = 51.1364 mph
- 200 ft/s = 136.364 mph
- 500 ft/s = 340.909 mph
- 2,000 ft/s = 1,363.64 mph
- 10,000 ft/s = 6,818.18 mph
Common slips when you convert ft/s to mph
The direction of the multiplication
If 88 ft/s turned into 129, you multiplied by 1.4667 instead of 0.6818. From ft/s to mph the figure must fall, and 88 ft/s is exactly 60 mph.
Reading ft/s as mph
A chronograph that shows 88 is not saying 88 mph. The mph figure is a third smaller. The confusion gives an error near 47 per cent.
Lost decimals
When the speed enters a squared formula, keep the decimals throughout and round only for display.
Short answers
How do I convert ft/s to mph?
Multiply the ft/s figure by 0.6818.
How many mph is 88 ft/s?
Exactly 60 mph.
How many mph is 100 ft/s?
68.18 mph.
How many ft/s is 1 mph?
1.4667 ft/s.
Does my number leave my device?
No, the calculation runs in your browser.
More pages and a wrap-up
For other speed conversions see Convert ft/s to m/s, Convert ft/s to km/h, Convert knots to mph, Convert m/s to mph, Convert mph to km/h, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. The reverse direction is Convert mph to ft/s.
To sum up, you convert ft/s to mph by multiplying by 0.6818 and writing the unit beside the result. Your number is processed locally, with no account and no upload.