About the Speed Converter
This speed converter changes a speed between the units people use most: miles per hour, kilometers per hour, meters per second, feet per second and knots, plus Mach number at sea level.
It's useful for road signs and car speedometers abroad, sports and running data, weather reports that give wind speed in knots or m/s, and physics homework. Enter a speed, pick the units, and see the answer along with a table of the same speed in every unit.
How to use it
- Type the speed in Value.
- Choose the unit you have in From, such as mph.
- Choose the unit you want in To, such as km/h.
- Read the answer and the conversion factor, or check the table for all units.
Conversion formula
Each unit is stored as a number of meters per second:
result = value × (m/s per From unit) ÷ (m/s per To unit)
- 1 km/h = 1/3.6 m/s (1,000 m in 3,600 s)
- 1 mph = 0.44704 m/s exactly (1,609.344 m in 3,600 s)
- 1 ft/s = 0.3048 m/s exactly
- 1 knot = 1 nautical mile per hour = 1,852/3,600 ≈ 0.514444 m/s
- Mach 1 is taken as 340.29 m/s, the standard speed of sound at sea level at 15 °C
The speed of sound depends on air temperature, so it's lower at cruising altitude where the air is colder. Treat Mach conversions here as a sea-level reference rather than an exact figure for an aircraft in flight.
Common speed conversions
| From | Equals |
|---|---|
| 30 mph | 48.28 km/h |
| 60 mph | 96.56 km/h = 26.82 m/s |
| 100 km/h | 62.14 mph |
| 1 m/s | 3.6 km/h = 2.23694 mph |
| 1 knot | 1.852 km/h = 1.15078 mph |
| 60 mph | 88 ft/s |
| Mach 1 (sea level) | 1,225.04 km/h = 761.21 mph |
Worked examples and quick tricks
Highway speed. 70 mph × 1.609344 = 112.65 km/h.
Wind speed. A forecast of 20 knots × 1.852 = 37.04 km/h, or about 23 mph.
Sprinting. Running 100 m in 10 seconds is 10 m/s, which is 36 km/h or about 22.37 mph.
Two handy mental shortcuts: to turn m/s into km/h, multiply by 3.6. To turn mph into ft/s, multiply by about 1.47, since 60 mph is exactly 88 feet per second. That second rule is useful for stopping-distance problems.
For running and cycling pace in minutes per mile or kilometer, the pace calculator is a better fit. For distances, use the length converter.
Frequently asked questions
How do I convert mph to km/h?
Multiply by 1.609344. For example, 50 mph × 1.609344 = 80.47 km/h.
How fast is 100 km/h in mph?
100 km/h is about 62.14 mph. To convert km/h to mph, divide by 1.609344.
What is a knot?
A knot is one nautical mile (1,852 m) per hour, which is 1.852 km/h or about 1.15 mph. It's used for ships, aircraft and wind speed.
How do I convert m/s to km/h?
Multiply by 3.6. So 25 m/s is 90 km/h.
How fast is Mach 1?
At sea level in standard conditions, Mach 1 is about 340.29 m/s, which is 1,225 km/h or about 761 mph. It's slower at high altitude, where the air is colder.
Last updated October 24, 2026. Results are estimates for education and planning — see our disclaimer.