Speed Converter
Convert km/h, mph, m/s, ft/s and knots for driving, running, wind, sailing and physics problems.
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How to use this tool
Steps for using the Unit Converter.
- Type a number into From — kilometers per hour are preselected. Commas and scientific notation such as 2.5e3 are accepted.
- Pick the units to convert between; the result in miles per hour (or whichever unit you choose) updates as you type. Use the swap button to reverse the conversion.
- Set the decimal places, turn on Show formula to see the calculation, and copy or share the result.
- Below the converter, the table lists every speed unit with its exact definition, and the links open dedicated pages for the most common pairs.
Example
100 kilometers per hour to miles per hour
100 km/h62.137119 mph
Formula: mph = km/h ÷ 1.609344Common use cases
- Speed limits and speedometers when driving abroad.
- Running and cycling paces.
- Wind speeds and boat or aircraft speeds in knots.
Speed unit table
| Unit | Symbol | System | Definition | In meters per second |
|---|---|---|---|---|
| Meter per second | m/s | SI | SI unit of speed | 1 |
| Kilometer per hour | km/h | Metric | 1,000 m in 3,600 s | 0.2777777778 |
| Mile per hour | mph | US customary | 1 mi in 1 h = exactly 0.44704 m/s | 0.44704 |
| Foot per second | ft/s | US customary | Exactly 0.3048 m/s | 0.3048 |
| Knot | kn | Other | 1 nautical mile per hour | 0.5144444444 |
Popular speed conversions
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About speed units
Speed is distance divided by time. The SI unit is the meter per second (m/s); km/h is used on roads in most countries and mph in the US and UK. Since a kilometer is 1,000 m and an hour 3,600 s, 1 m/s = exactly 3.6 km/h.
One mph is exactly 0.44704 m/s (1,609.344 m in 3,600 s), which makes 1 mph ≈ 1.609 km/h. The knot — one nautical mile per hour, about 1.151 mph — is the standard unit for ships, aircraft and wind speeds in aviation weather reports.
Limitations
- Results are rounded for display only; the calculation keeps full precision (15 significant digits).
Frequently asked questions
How do I convert km/h to mph quickly?
Divide by 1.609 — or multiply by about 0.62. 100 km/h ≈ 62.1 mph.
How do I convert m/s to km/h?
Multiply by exactly 3.6: 10 m/s = 36 km/h.
What is a knot in km/h?
Exactly 1.852 km/h, because a knot is one nautical mile (1,852 m) per hour.
Are these speed conversions exact?
Each unit is defined from its official definition (for example 1 inch = 2.54 cm exactly). Results are calculated in double precision and only rounded to the decimal places you choose when shown.