Room for ChanceWhat it measures and where it is used
Length measures distance or size, from a component’s thickness to a journey. The metre replaced many local standards and is now defined using the speed of light. One international inch equals exactly 2.54 centimetres; the international foot is used here.
- Classification
- SI base quantity
- SI unit
- m
- Dimension
- L
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
1 in ≈ 2.54 cm
Available units
Reference unit: m
| Available units | Reference factor |
|---|---|
| m | 1 × x |
| km | 1,000 × x |
| cm | 0.01 × x |
| mm | 0.001 × x |
| µm | 0.000001 × x |
| nm | 0.000000001 × x |
| in | 0.0254 × x |
| ft | 0.3048 × x |
| yd | 0.9144 × x |
| mi | 1,609.344 × x |
| nmi | 1,852 × 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.