Common unit conversions made simple
Recipes, travel, shopping and school all mix metric and imperial units. A few reference values and one or two tricks cover most everyday conversions.
Length
The metric system works in tens, so moving between centimeters, meters and kilometers just means shifting the decimal point. Between systems, remember these exact values:
| Unit | Equals |
|---|---|
| 1 inch | 2.54 centimeters |
| 1 foot | 0.3048 meters |
| 1 yard | 0.9144 meters |
| 1 mile | 1.609344 kilometers |
A mental shortcut for miles to kilometers: multiply by 1.6. So 10 miles is about 16 km. For kilometers to miles, multiply by 0.62.
Weight
One kilogram is 1,000 grams, and one metric tonne is 1,000 kilograms. For imperial units, 1 pound is 0.45359237 kg and 1 ounce is about 28.35 g. A quick rule: kilograms × 2.2 gives pounds. A 70 kg person weighs about 154 lb.
Temperature
Temperature needs a formula because each scale starts from a different zero.
- Celsius to Fahrenheit: multiply by 9/5, then add 32.
- Fahrenheit to Celsius: subtract 32, then multiply by 5/9.
- Celsius to Kelvin: add 273.15.
Useful anchors: water freezes at 0 °C (32 °F) and boils at 100 °C (212 °F) at sea level. Normal body temperature is about 37 °C or 98.6 °F. The two scales meet at −40, where −40 °C equals −40 °F.
Currency
Currency is different again because rates change every day. Use a recent reference rate, then expect your bank or exchange to charge a fee or use a slightly worse rate. Several Gulf currencies, including the Omani rial, are pegged to the US dollar, so those rates stay stable.
Everyday examples
A car travelling at 100 km/h is going about 62 mph. A person who is 5 ft 9 in tall is 69 inches, which is about 175 cm. A suitcase limit of 23 kg is roughly 50.7 lb. A fever reading of 38.5 °C is 101.3 °F. Knowing a few of these anchor values lets you sanity-check any result you see.
Tips to avoid errors
- Write the unit next to every number so you do not mix them up.
- Do a quick estimate first. If 10 miles comes out as 6 km, something is wrong.
- Do not round too early in a multi-step conversion.
Skip the maths with the unit and currency converter.
Related pages
Unit and currency converter
Convert length, weight, temperature, currency.
Basic calculator
Everyday sums.
Converter FAQ
14 quick answers.
Related blog posts and countries
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