Speed Converter
Convert km/h, mph, m/s, knots and ft/s — including Mach at sea level.
The Speed Converter translates between the units that cars, planes, boats, weather reports and physics classes use: kilometers per hour, miles per hour, meters per second, feet per second, knots and Mach (at standard sea-level conditions).
The classic confusion is road speed: 100 km/h is about 62 mph (the factor is 0.621371), and every European driving a US rental car, or American driving in Canada, meets it at the first speed-limit sign. Runners and cyclists switch between km/h and min-per-km pace thinking; sailors and pilots think in knots; meteorologists in m/s for wind gusts.
Each unit is defined exactly against meters per second (1 mph = 0.44704 m/s, 1 knot = 0.514444 m/s), so results are precise. Mach is shown for standard sea-level conditions (340.29 m/s) as an approximation, since true Mach depends on temperature and altitude.
Result
1 km/h = 0.621371192237 mph
1 km/h = 0.621371192237 mph
1 mph = 1.609344 km/h
How to use the Speed Converter
- Type the speed value.
- Pick the source unit — km/h, mph, m/s, kn, ft/s or Mach.
- Pick the target unit.
- Read the converted speed and the unit rate.
- Use swap to convert the other way around.
Frequently asked questions
How do I convert km/h to mph?
Multiply by 0.621371: 100 km/h × 0.621371 = 62.14 mph. Going the other way, multiply mph by 1.609344. A quick mental trick: 60 mph ≈ 100 km/h, 30 mph ≈ 50 km/h.
How many mph is a knot?
One knot is 1.15078 mph (or 1.852 km/h). Knots are nautical miles per hour, used by ships, aircraft and wind forecasts — a 30-knot wind is about 34.5 mph, which is a full gale.
Is Mach 1 always the same speed?
No — Mach 1 is the local speed of sound, which depends on air temperature and altitude (about 340 m/s at sea level, slower at altitude in cold air). This converter uses the standard sea-level figure of 340.29 m/s, which is the convention for casual reference.
Related tools
View all unit converters →Length Converter
Convert between metric and imperial lengths: mm to inches, km to miles and more.
ConvertersWeight Converter
Convert kilograms, pounds, ounces, grams, stones and tons instantly.
ConvertersHeight Converter
Height in cm, meters or feet & inches — with the feet-inches split done for you.
ConvertersTemperature Converter
Convert Celsius, Fahrenheit, Kelvin and Rankine with one click.
ConvertersArea Converter
Convert square meters, square feet, acres, hectares and more.
ConvertersVolume Converter
Convert liters, gallons (US & UK), cups, cubic feet, barrels and more.