Everyday world · Updated September 2026
Metric vs imperial
Metric (SI) uses metres, kilograms and Celsius. The US customary system still uses miles, pounds and Fahrenheit. How to convert the units people search every day.
The metric system (SI) is the world standard for science and for most countries: metre, kilogram, litre, Celsius (and kelvin in labs). The United States still uses customary units for road signs, cooking and body height — miles, pounds, ounces, Fahrenheit.
The UK is mixed: road distances in miles, milk sometimes in pints, official science and most shops in metric. Canada and Australia completed metrication decades ago but older people still think in pounds and Fahrenheit.
Useful conversions: 1 mile ≈ 1.609 km; 1 inch = 2.54 cm; 1 kg ≈ 2.205 lb; °C to °F is (°C × 9/5) + 32. Open the dedicated Celsius page for more examples.
Metric vs imperial — key facts (2026)
| Topic | Fact |
|---|---|
| SI length | Metre (m) |
| SI mass | Kilogram (kg) |
| US road unit | Mile |
| 1 mile | 1.609344 km |
| 1 inch | 2.54 cm exactly |
| 1 kilogram | About 2.205 pounds |
| Water freeze | 0 °C = 32 °F |
| Water boil (1 atm) | 100 °C = 212 °F |
Figures are the usual classroom and news-desk numbers for 2026. Border disputes and membership votes can change a count by one or two.
People also ask
Which countries use the imperial system?
The US is the large hold-out for everyday life. Liberia and Myanmar have mixed stories. The UK uses both. Science is metric almost everywhere.
How do I convert miles to kilometres?
Multiply miles by 1.609. Five miles is about 8 km.
Is Celsius metric?
Celsius is the everyday temperature scale used with metric. The SI thermodynamic scale is kelvin.