How to use the speed converter
Pick the unit you have in From and the unit you want in To, type the value and press Convert. Swap units reverses the direction. Speeds here are magnitudes, so negative values are rejected; zero is accepted.
How speed conversion works
Every speed unit is a distance divided by a time, so each one is a fixed multiple of the SI unit, the meter per second (m/s). The converter turns your value into meters per second and then into the target unit. The factors come from exact definitions rather than rounded numbers:
- Kilometer per hour: 1,000 m in 3,600 s, so 1 m/s is exactly 3.6 km/h.
- Mile per hour: the international mile is exactly 1,609.344 m, so 1 mph is exactly 1.609344 km/h, or 0.44704 m/s. The United States and the United Kingdom use the same mile.
- Knot: one nautical mile per hour. The international nautical mile is exactly 1,852 m, so 1 knot is exactly 1.852 km/h, about 1.151 mph.
- Foot per second: the foot is exactly 0.3048 m, so 1 ft/s is exactly 1.09728 km/h.
- Speed of light (c): exactly 299,792,458 m/s, the value that has defined the meter since 1983.
Common speed conversion factors
Multiply a value in the first unit by the factor to get the second unit.
| From | To | Multiply by | Note |
|---|---|---|---|
| km/h | mph | 0.621371 | 1 ÷ 1.609344, rounded |
| mph | km/h | 1.609344 | exact |
| m/s | km/h | 3.6 | exact |
| mph | m/s | 0.44704 | exact |
| kn | km/h | 1.852 | exact |
| kn | mph | 1.150779 | rounded |
| km/h | kn | 0.539957 | rounded |
| ft/s | km/h | 1.09728 | exact |
| mph | ft/s | 1.466667 | 22/15, rounded |
Worked examples
- 100 km/h to mph: 100 × 0.621371 ≈ 62.14 mph.
- 70 mph to km/h: 70 × 1.609344 = 112.65408 km/h, about 112.7 km/h.
- 25 knots to km/h: 25 × 1.852 = 46.3 km/h, which is about 28.77 mph.
- 10 m/s to km/h: 10 × 3.6 = 36 km/h. To go back, divide by 3.6.
Kilometers per hour to miles per hour
| km/h | mph | kn | m/s |
|---|---|---|---|
| 10 | 6.21 | 5.4 | 2.78 |
| 20 | 12.43 | 10.8 | 5.56 |
| 30 | 18.64 | 16.2 | 8.33 |
| 40 | 24.85 | 21.6 | 11.11 |
| 50 | 31.07 | 27 | 13.89 |
| 60 | 37.28 | 32.4 | 16.67 |
| 70 | 43.5 | 37.8 | 19.44 |
| 80 | 49.71 | 43.2 | 22.22 |
| 90 | 55.92 | 48.6 | 25 |
| 100 | 62.14 | 54 | 27.78 |
| 110 | 68.35 | 59.4 | 30.56 |
| 120 | 74.56 | 64.79 | 33.33 |
| 130 | 80.78 | 70.19 | 36.11 |
Miles per hour to kilometers per hour
| mph | km/h | kn | m/s |
|---|---|---|---|
| 5 | 8.05 | 4.34 | 2.24 |
| 10 | 16.09 | 8.69 | 4.47 |
| 15 | 24.14 | 13.03 | 6.71 |
| 20 | 32.19 | 17.38 | 8.94 |
| 25 | 40.23 | 21.72 | 11.18 |
| 30 | 48.28 | 26.07 | 13.41 |
| 35 | 56.33 | 30.41 | 15.65 |
| 40 | 64.37 | 34.76 | 17.88 |
| 45 | 72.42 | 39.1 | 20.12 |
| 50 | 80.47 | 43.45 | 22.35 |
| 55 | 88.51 | 47.79 | 24.59 |
| 60 | 96.56 | 52.14 | 26.82 |
| 65 | 104.61 | 56.48 | 29.06 |
| 70 | 112.65 | 60.83 | 31.29 |
| 75 | 120.7 | 65.17 | 33.53 |
| 80 | 128.75 | 69.52 | 35.76 |
Knots, nautical miles and aviation
Ships and aircraft measure speed in knots because charts measure distance in nautical miles. The nautical mile was originally tied to one minute of latitude, which makes distances easy to read off a chart; it is now fixed at exactly 1,852 m. A knot already means "per hour", so "knots per hour" is a mistake: it would describe an acceleration, not a speed. Wind speeds in marine and aviation weather reports are also commonly given in knots.
| kn | km/h | mph | m/s |
|---|---|---|---|
| 1 | 1.85 | 1.15 | 0.51 |
| 5 | 9.26 | 5.75 | 2.57 |
| 10 | 18.52 | 11.51 | 5.14 |
| 15 | 27.78 | 17.26 | 7.72 |
| 20 | 37.04 | 23.02 | 10.29 |
| 30 | 55.56 | 34.52 | 15.43 |
| 40 | 74.08 | 46.03 | 20.58 |
| 50 | 92.6 | 57.54 | 25.72 |
| 100 | 185.2 | 115.08 | 51.44 |
| 250 | 463 | 287.69 | 128.61 |
| 500 | 926 | 575.39 | 257.22 |
Why Mach is only an approximation
A Mach number is a speed divided by the local speed of sound, and the speed of sound in air depends on the air temperature, not on a fixed distance per time. This converter uses 340.294 m/s, the value for the International Standard Atmosphere at sea level and 15 °C, so Mach 1 is shown as about 1,225.06 km/h or 761.22 mph.
At cruising altitude the air is much colder. In the standard atmosphere the temperature at the tropopause is −56.5 °C, where sound travels at about 295 m/s (about 1,062 km/h). An airliner with a true airspeed of 900 km/h is about Mach 0.85 in that air, while the converter, using the sea-level value, would show about Mach 0.73. Use the Mach unit for rough comparisons, not for flight planning.
Common pitfalls
- Rounding the mile to 1.6 km. Dividing by 1.6 is a handy mental shortcut but it overstates speeds in mph by about 0.58%: 120 km/h ÷ 1.6 gives 75 mph, while the exact answer is about 74.56 mph.
- Confusing nautical and statute miles. A nautical mile is about 15% longer than a statute mile, so a boat doing 20 knots is faster than a car doing 20 mph.
- Treating pace as a speed unit. Runners often use minutes per kilometer or per mile. Pace is the reciprocal of speed and is not offered here, but it is easy to derive: 12 km/h is 60 ÷ 12 = 5 minutes per kilometer.
- Mixing per-minute and per-second units. Feet per minute is common for vertical speeds in aviation and for air velocity in ducts. 500 ft/min is only 2.54 m/s, or 9.144 km/h.
Frequently asked questions
How many km/h is 60 mph?
60 × 1.609344 = 96.56064 km/h, so about 96.6 km/h.
Is a knot faster than a mile per hour?
Yes. One knot is 1.852 km/h and one mile per hour is 1.609344 km/h, so a knot is about 1.151 mph.
How do I convert m/s to km/h in my head?
Multiply by 3.6, which is exact. For the reverse, divide by 3.6: 90 km/h is 25 m/s.
Why can't I enter a negative speed?
The converter works with speed as a magnitude, which cannot be below zero. If you are working with a velocity that has a direction, convert the magnitude and keep the sign yourself; every unit here is a plain multiple of the others, so the sign does not change.
Does the United Kingdom use a different mile per hour?
No. Road speeds in the UK are in miles per hour, and the mile is the same international mile of 1,609.344 m used in the United States.
Supported units
- Meter per second (m/s)
- Kilometer per hour (km/h)
- Mile per hour (mph)
- Knot (kn)
- Foot per second (ft/s)
- Foot per minute (ft/min)
- Meter per minute (m/min)
- Kilometer per second (km/s)
- Centimeter per second (cm/s)
- Inch per second (in/s)
- Mach (sea level, 15 °C) (Mach)
- Speed of light (c)