US Customary vs Metric
Last updated February 14, 2026 · Length
The United States is the largest economy still using a non-metric system for everyday measurement. US customary units govern road signs, weather forecasts, grocery packaging, construction and cooking, while science, medicine, the military and most manufacturing use metric.
The units you meet daily
- Distance — inches, feet, yards and miles; speed in miles per hour
- Weight — ounces and pounds; short tons for freight
- Volume — fluid ounces, cups, pints, quarts and US gallons
- Temperature — degrees Fahrenheit
- Area — square feet for buildings, acres for land
Exact conversion factors
| US customary | Metric equivalent |
|---|---|
| 1 inch | 2.54 cm |
| 1 foot | 0.3048 m |
| 1 yard | 0.9144 m |
| 1 mile | 1.609344 km |
| 1 ounce | 28.349523125 g |
| 1 pound | 0.45359237 kg |
| 1 US gallon | 3.785411784 L |
| 1 acre | 4,046.8564224 m² |
The overlap that catches people out
US customary length units are identical to Imperial ones, so a US foot and a UK foot are the same. Volume and the ton are not: always check whether a gallon, pint, fluid ounce or ton is US or Imperial before converting.