5 min read
2026-03-11
Two main systems are used in the world: the **metric** (SI) and **imperial** (USA, UK) systems.
| Unit | Abbreviation | Relationship |
|---|---|---|
| Nanometer | nm | 10⁻⁹ m |
| Micrometer | µm | 10⁻⁶ m |
| Millimeter | mm | 0.001 m |
| Centimeter | cm | 0.01 m |
| Decimeter | dm | 0.1 m |
| Meter | m | base unit |
| Kilometer | km | 1,000 m |
| Unit | Abbreviation | In Meters |
|---|---|---|
| Inch | in / ″ | 0.0254 m |
| Foot | ft / ′ | 0.3048 m |
| Yard | yd | 0.9144 m |
| Mile | mi | 1,609.344 m |
| Nautical mile | nmi | 1,852 m |
**Construction and renovation:** American products list dimensions in inches — conversion is needed when buying materials.
**Travel:** Road signs in the US and UK are in miles, and speed is in miles per hour.
**Sports:** Running uses both kilometers and miles (marathon = 42.195 km = 26.219 miles).
**Aviation and maritime:** Altitudes are in feet, distances in nautical miles.
Convert any length units with the Length Converter.
See also: Weight Converter, Speed Converter, Temperature Converter