Calculator
Speed (m/s)10.4384 m/s
Speed (km/h)37.5783 km/h
Method, variables and units
Speed Calculator
Formula: v = d / t
Assumption: Distance and time describe the same interval, and time is greater than zero.
Worked example
Speed Calculator
100 m in 9.58 s is 10.44 m/s, or 37.46 km/h.
Everyday speeds compared
| Example | m/s | km/h | mph |
|---|---|---|---|
| Walking pace | 1.4 | 5 | 3.1 |
| Recreational cycling | 5 | 18 | 11.2 |
| 100 m world record (Bolt, 2009) | 10.44 | 37.6 | 23.4 |
| Car on a 50 km/h street | 13.89 | 50 | 31.1 |
| Motorway at 120 km/h | 33.33 | 120 | 74.6 |
| Speed of sound in air at 20 °C | 343 | 1,234.8 | 767.3 |
To convert, multiply m/s by 3.6 for km/h, or divide by 0.44704 for mph (1 mile per hour is exactly 0.44704 m/s). Average speed over a trip with stops is total distance divided by total time: a 120 km journey that takes 1 h 30 min including a 15-minute break averages 120 / 1.5 = 80 km/h, even if the car never drove at exactly that speed.
Common mistakes
- Averaging two speeds directly: driving 60 km/h one way and 40 km/h back over the same distance averages 48 km/h, not 50 km/h, because more time is spent at the slower speed.
- Mixing units: distance in kilometres with time in seconds gives km/s, not km/h.
- Treating speed as velocity: speed has no direction, so a round trip back to the start has an average velocity of zero but a non-zero average speed.