Unit & Measurement Tables
Speed Conversion Table
Speed conversions look simple until you notice that there are three different miles and two different hours in play. The mile used on the road is the statute mile of 1,609.344 m, agreed internationally in 1959. The mile used at sea is the nautical mile of 1,852 m, which is one minute of latitude and has no simple relationship to the land mile. Conflating the two produces a 15% error that no amount of care downstream will remove.
The second trap is the hour in metres per second. Converting km/h to m/s is a factor of 3.6 — a thousand metres in a kilometre and 3,600 seconds in an hour — and people who remember only "divide by something" often use 3.6 on miles instead of kilometres. The correct factor for mph to m/s is 0.44704, from the exact 1.609344 km per mile.
Everything below is derived from the exact definitions rather than from a rounded chain of conversions, so a figure read here matches what a physics textbook or a calibrated instrument reports. The tables run from walking pace to motorway speed in both directions, which covers most of what people actually need to convert.
Miles per hour to km/h, knots, m/s and ft/s
| mph | km/h | knots | m/s | ft/s |
|---|---|---|---|---|
| 5 | 8.05 | 4.34 | 2.24 | 7.33 |
| 10 | 16.09 | 8.69 | 4.47 | 14.67 |
| 15 | 24.14 | 13.03 | 6.71 | 22.00 |
| 20 | 32.19 | 17.38 | 8.94 | 29.33 |
| 25 | 40.23 | 21.72 | 11.18 | 36.67 |
| 30 | 48.28 | 26.07 | 13.41 | 44.00 |
| 35 | 56.33 | 30.41 | 15.65 | 51.33 |
| 40 | 64.37 | 34.76 | 17.88 | 58.67 |
| 45 | 72.42 | 39.10 | 20.12 | 66.00 |
| 50 | 80.47 | 43.45 | 22.35 | 73.33 |
| 55 | 88.51 | 47.79 | 24.59 | 80.67 |
| 60 | 96.56 | 52.14 | 26.82 | 88.00 |
| 65 | 104.61 | 56.48 | 29.06 | 95.33 |
| 70 | 112.65 | 60.83 | 31.29 | 102.67 |
| 75 | 120.70 | 65.17 | 33.53 | 110.00 |
| 80 | 128.75 | 69.52 | 35.76 | 117.33 |
A statute mile is 1.609344 km exactly, so every figure here is exact to the decimals shown rather than rounded from an approximation.
Kilometres per hour to mph, knots, m/s and ft/s
| km/h | mph | knots | m/s | ft/s |
|---|---|---|---|---|
| 10 | 6.21 | 5.40 | 2.78 | 9.11 |
| 20 | 12.43 | 10.80 | 5.56 | 18.23 |
| 30 | 18.64 | 16.20 | 8.33 | 27.34 |
| 40 | 24.85 | 21.60 | 11.11 | 36.45 |
| 50 | 31.07 | 27.00 | 13.89 | 45.57 |
| 60 | 37.28 | 32.40 | 16.67 | 54.68 |
| 70 | 43.50 | 37.80 | 19.44 | 63.79 |
| 80 | 49.71 | 43.20 | 22.22 | 72.91 |
| 90 | 55.92 | 48.60 | 25.00 | 82.02 |
| 100 | 62.14 | 54.00 | 27.78 | 91.13 |
| 120 | 74.56 | 64.79 | 33.33 | 109.36 |
| 140 | 86.99 | 75.59 | 38.89 | 127.59 |
| 160 | 99.42 | 86.39 | 44.44 | 145.82 |
| 180 | 111.85 | 97.19 | 50.00 | 164.04 |
| 200 | 124.27 | 107.99 | 55.56 | 182.27 |
Dividing km/h by 3.6 gives m/s directly, since a kilometre is 1,000 m and an hour is 3,600 s.
Exact conversion factors
| Unit | In km/h | In m/s | In mph |
|---|---|---|---|
| 1 mph | 1.609344 | 0.447040 | 1 |
| 1 km/h | 1 | 0.277778 | 0.621371 |
| 1 knot | 1.852000 | 0.514444 | 1.150779 |
| 1 m/s | 3.600000 | 1 | 2.236936 |
| 1 ft/s | 1.609344 | 1.097280 | 0.681818 |
The knot is a nautical mile per hour and the mile here is the statute mile — the two differ by about 15%, which is why wind and sea speeds never agree with road speeds.
How to Use These Tables
- Road speed: multiply mph by 1.609344 for km/h, or divide km/h by 1.609344 for mph. 70 mph is 112.65 km/h.
- Wind and sea: knots to km/h is × 1.852, knots to mph is × 1.15078. A 20 knot wind is 23.02 mph.
- Physics work: convert to m/s before using any formula, since SI formulas assume metres and seconds. 50 km/h is 13.89 m/s.
- Running and cycling pace: pace is the reciprocal of speed. 10 km/h is a 6.00 min/km split, and dividing 60 by the km/h figure gives minutes per kilometre.
Common Questions
Why is a knot not the same as a mile per hour?
A knot is one nautical mile per hour and a nautical mile is 1,852 m, against 1,609.344 m for the statute mile. One knot is 1.15078 mph, so a 20 knot wind is about 23 mph, not 20.
How do I convert km/h to m/s quickly?
Divide by 3.6. There are 1,000 m in a kilometre and 3,600 s in an hour, so 3,600 ÷ 1,000 = 3.6. Going the other way, multiply m/s by 3.6.
Is the 1.609344 figure exact?
Yes. The 1959 international yard and pound agreement defined the yard as 0.9144 m exactly, which makes the mile 1,609.344 m exactly. Any conversion using a different figure is rounded, however many decimals it shows.
What speed is the speed of sound?
About 343 m/s at 20 °C at sea level, which is 1,235 km/h or 767 mph. It varies with air temperature, not with altitude directly, which is why the Mach number is defined against local conditions.
How do I convert a pace to a speed?
Divide 60 by the minutes per kilometre: a 5 min/km pace is 12 km/h. For miles per hour, divide 60 by minutes per mile; a 8 min/mile pace is 7.5 mph, which is 12.07 km/h.
More Unit & Measurement Tables
Sources
- NIST Special Publication 811 — units outside the SI, including the knot — National Institute of Standards and Technology
- Refinement of values for the yard and the pound (1959 agreement) — National Bureau of Standards
- Speed conversions and unit definitions — National Institute of Standards and Technology
Filed with Unit Conversion calculations.