The SI unit of speed is the metre per second (m/s or m·s−1).
Definition and formula
Speed is the rate of change of distance with respect to time.
Formula:v = d/t, where d is distance in metres (m) and t is time in seconds (s).
Dimension: L T−1 | Dimensional formula: [M0L1T−1]
Related units
- SI coherent unit: m/s
- Common non-SI unit accepted with SI: kilometre per hour (km/h)
Key conversions
| Relation | Value |
| 1 m/s in km/h | 3.6 km/h |
| 1 km/h in m/s | 0.277 777… m/s |
| 1 mph in m/s | 0.447 04 m/s |
| 1 m/s in mph | 2.236 94 mph |
Useful scales
- mm/s = 10−3 m/s
- cm/s = 10−2 m/s
- km/s = 103 m/s
Quick examples
- 108 km/h = 108 × 0.277 777… = 30 m/s
- 12 m/s = 12 × 3.6 = 43.2 km/h
