🚀 Speed Converter
Convert mph, km/h, m/s, knots and Mach at once — handy for driving abroad, wind speeds and aircraft.
Common speed conversions
| Value | mph | km/h | m/s | kn | Note |
|---|---|---|---|---|---|
| 3 mph | 3 | 4.828 | 1.3411 | 2.6069 | walking pace |
| 25 mph | 25 | 40.234 | 11.176 | 21.724 | US residential speed limit |
| 50 km/h | 31.069 | 50 | 13.889 | 26.998 | typical city limit outside the US |
| 65 mph | 65 | 104.61 | 29.058 | 56.483 | US highway limit |
| 100 km/h | 62.137 | 100 | 27.778 | 53.996 | highway limit in many countries |
| 130 km/h | 80.778 | 130 | 36.111 | 70.194 | French / German autobahn advisory |
| 39 mph | 39 | 62.764 | 17.435 | 33.89 | tropical storm winds begin |
| 74 mph | 74 | 119.09 | 33.081 | 64.304 | hurricane (Category 1) begins |
| 1 kn | 1.1508 | 1.852 | 0.51444 | 1 | ships and aircraft |
| 550 mph | 550 | 885.14 | 245.87 | 477.94 | airliner cruise, roughly |
| 1 Mach | 761.21 | 1,225 | 340.29 | 661.47 | speed of sound (15 °C, sea level) |
How to use the speed converter
Enter a speed and unit to convert it into mph, km/h, m/s, knots, ft/s and Mach at the same time. Use it when renting a car abroad (speed limits in km/h), reading wind speeds in m/s or knots, or comparing running and cycling paces.
Speed units at a glance
| Unit | Symbol | Definition |
|---|---|---|
| Meters per second | m/s | SI unit |
| Kilometers per hour | km/h | 1 m/s = 3.6 km/h |
| Miles per hour | mph | ≈ 1.609 km/h |
| Knot | kn | 1 nautical mile per hour = 1.852 km/h |
| Feet per second | ft/s | 0.3048 m/s |
| Mach (approx.) | Mach | Speed of sound at sea level, 15 °C ≈ 340.29 m/s |
How to convert speed
Every unit is converted to meters per second, then to the target unit.
km/h = mph × 1.609344mph = km/h × 0.621371km/h = m/s × 3.6— one hour is 3,600 seconds and a kilometer is 1,000 metersmph = knots × 1.15078km/h = knots × 1.852Mach = speed ÷ local speed of sound— approximated here as 340.29 m/s (about 761 mph)
Driving abroad
Outside the US and UK, speed limits are posted in km/h. Handy pairs: 50 km/h ≈ 31 mph (city), 80 km/h ≈ 50 mph, 100 km/h ≈ 62 mph, 120 km/h ≈ 75 mph. A quick estimate is km/h × 0.6 for mph, or mph × 1.6 for km/h.
Wind speeds
The US National Weather Service reports wind in mph, aviation and marine forecasts use knots, and many other countries use m/s or km/h. On the Saffir-Simpson scale a hurricane starts at 74 mph (64 knots, 119 km/h, 33 m/s), and a tropical storm at 39 mph (34 knots).
Why Mach is approximate
A Mach number is speed divided by the speed of sound where the object is. Sound travels about 340 m/s at sea level and 15 °C, but only about 295 m/s at airliner cruising altitude (around −50 °C). The same speed is therefore a higher Mach number at altitude.
Speed limits and storm thresholds are examples and vary by road and agency. Follow posted signs and official forecasts.