Room for ChanceWhat it measures and where it is used
Speed is distance travelled per unit time. Metres per second are used in physics; kilometres per hour and miles per hour are common in transport. A knot means one nautical mile per hour, reflecting its maritime origin; it is not one kilometre per hour.
- Classification
- SI derived quantity
- SI unit
- m/s
- Dimension
- L T⁻¹
L: length; M: mass; T: time; Θ: temperature; N: amount of substance. The dimension symbol N is not the unit symbol for newton.
How it works
The calculation first converts to a common reference unit, then to the destination unit. Factors in the table show the reference value for one unit.
Example
100 km/h ≈ 62.1371192237 mph
Available units
Reference unit: m/s
| Available units | Reference factor |
|---|---|
| m/s | 1 × x |
| km/h | 0.277777777778 × x |
| mph | 0.44704 × x |
| kn | 0.514444444444 × x |
| ft/s | 0.3048 × x |
| cm/s | 0.01 × x |
Units, history and conventions
The International System of Units (SI) received its name in 1960. Since the 2019 revision, its definitions use fixed values of seven defining constants. SI base and derived quantities should not be confused with the different units used to express them.