km/h · mph · m/s · kn
Speed converter
One mile per hour is exactly 1.609344 km/h, and one knot is exactly 1.852 km/h. Enter a speed, pick a unit and read it in all six units at once.
- 1 km/h = 0.6213712 mph
- 1 mph = 1.609344 km/h
The result and the table below it update as you type. Only the printed figure is rounded, to six significant digits, so a rounded value is never carried into the next conversion.
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At a glance
- Price
- No charge
- Account
- None needed
- Upload
- Not applicable — you type a value, nothing is sent anywhere
- Units
- Metre per second, kilometre per hour, mile per hour, knot, foot per second and Mach
- Precision
- Exact factors, printed to six significant digits; Mach is fixed at 340.29 m/s
- Works on
- Any modern browser
Common speed conversions
These tables are computed from the same factors as the converter. Read each one left to right: the first column is the value you start with and the second is its equivalent.
| km/h | mph |
|---|---|
| 1 | 0.621371 |
| 10 | 6.21371 |
| 50 | 31.0686 |
| 100 | 62.1371 |
| 200 | 124.274 |
| mph | km/h |
|---|---|
| 1 | 1.60934 |
| 10 | 16.0934 |
| 50 | 80.4672 |
| 100 | 160.934 |
| 200 | 321.869 |
| m/s | km/h |
|---|---|
| 1 | 3.6 |
| 10 | 36 |
| 50 | 180 |
| 100 | 360 |
| 200 | 720 |
| km/h | m/s |
|---|---|
| 1 | 0.277778 |
| 10 | 2.77778 |
| 50 | 13.8889 |
| 100 | 27.7778 |
| 200 | 55.5556 |
| kn | km/h |
|---|---|
| 1 | 1.852 |
| 10 | 18.52 |
| 50 | 92.6 |
| 100 | 185.2 |
| 200 | 370.4 |
| km/h | kn |
|---|---|
| 1 | 0.539957 |
| 10 | 5.39957 |
| 50 | 26.9978 |
| 100 | 53.9957 |
| 200 | 107.991 |
Speed units and their exact size
| Unit | Symbol | Exact size |
|---|---|---|
| Metre per second | m/s | 1 m/s = 1 m/s |
| Kilometre per hour | km/h | 1 km/h = 0.277777777777778 m/s |
| Mile per hour | mph | 1 mph = 0.44704 m/s |
| Knot | kn | 1 kn = 0.514444444444444 m/s |
| Foot per second | ft/s | 1 ft/s = 0.3048 m/s |
| Mach | Ma | 1 Ma = 340.29 m/s |
How to convert a speed
Enter the speed
Type a number in the first field. Negative values and decimals are accepted, so 12.5 and −3 both work.
Pick the two units
Choose the unit you have in the first menu and the unit you want in the second. The swap button reverses the two.
Read the table
The large figure is your answer. The table lists the same speed in every other unit, so you can copy the one you need without converting again.
How speed conversion works
Every unit on this page is defined from the metre per second. A kilometre per hour is 1000 m in 3600 s, so exactly 1/3.6 m/s. A mile per hour is exactly 0.44704 m/s, because the international mile is 1609.344 m. A knot is one nautical mile of 1852 m per hour, which is 1852/3600 m/s, about 0.514444 m/s. A foot per second is exactly 0.3048 m/s. Mach is the one approximate unit: this page fixes it at 340.29 m/s.
A conversion is a multiplication and a division: the value times the source unit's size in metres per second, divided by the target unit's. Kilometres per hour to miles per hour is value ÷ 1.609344, which is value × 0.621371 to six digits, and metres per second to kilometres per hour is value × 3.6. Because the factors are exact, the only rounding is in the figure printed. The exception is Mach: the real speed of sound varies with temperature and altitude, so a Mach result is only as accurate as the fixed 340.29 m/s.
Speed conversion questions
How many mph is 100 km/h?
100 km/h is 62.1371 mph. One mile per hour is exactly 1.609344 km/h, so divide kilometres per hour by 1.609344 to get miles per hour, or multiply miles per hour by 1.609344 to get kilometres per hour: 60 mph is 96.56064 km/h.
How many mph and km/h is a knot?
One knot is exactly 1.852 km/h, about 1.15078 mph, because a knot is one nautical mile (1852 m) per hour. So 20 knots is 37.04 km/h, or about 23.0156 mph, and 10 knots is 18.52 km/h.
Is Mach 1 always the same speed?
No. Mach is a ratio to the local speed of sound, and that speed varies with air temperature and altitude. This page uses one fixed value, 340.29 m/s, the speed of sound near sea level at 15 °C in the standard atmosphere. That makes Mach 1 equal to 1225.044 km/h, or about 761.207 mph.
Do my numbers leave my device?
No. The unit tables are part of the page and the arithmetic runs in your browser, so nothing you type is sent anywhere. With the page already loaded, the converter also works offline.
How precise are the results?
Results are computed in double precision from exact factors and printed to six significant digits; the unit table shows twelve. Values below 1e-6 or at 1e15 and above switch to exponent form so they stay readable.