Unit Converter
Choose a type of unit, pick the two units and type a value. You get the converted value instantly, with a table of common values.
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The formula
Result = value x (size of the "from" unit / size of the "to" unit).
How to use the converter
Pick the type of unit first (length, weight, temperature and so on), then choose the two units and type a value. The result updates as you type, and a table beside it shows common values so you can see the pattern.
What you can convert
- Length: mm, cm, m, km, inches, feet, yards, miles
- Weight: mg, g, kg, tonnes, ounces, pounds, stone
- Volume and cooking: ml, litres, teaspoons, tablespoons, cups, pints, gallons
- Area, speed, time, pressure, power, energy, angle and data
For popular pairs such as cm to inches or kg to lbs there are dedicated pages with extra tips, and size converters for rings, shoes and clothing.
The most-used length conversions
| From | To |
|---|---|
| 1 in | 2.54 cm |
| 1 cm | 0.3937 in |
| 1 ft | 0.3048 m |
| 1 m | 3.2808 ft |
| 1 mi | 1.6093 km |
| 1 km | 0.62137 mi |
| 1 yd | 0.9144 m |
| 1 ft | 30.48 cm |
| 1 mm | 0.03937 in |
Use these as a sanity check. If your answer is far from the table, the units are probably the wrong way round.
Why the answers are exact
Conversions use the internationally agreed definitions, for example 1 inch = 25.4 mm exactly and 1 pound = 0.45359237 kg exactly. We keep full precision internally and only round the number you see.
Unit Converter: frequently asked questions
Can I convert in both directions?
Yes. Swap the From and To units and the answer follows.
How many decimal places are shown?
Up to 10 significant decimals for the main result, with common-value tables rounded to about 8.
Does the converter need an internet connection?
Not once the page has loaded. The calculation happens in your browser.
How exact is the conversion?
It uses the internationally agreed definitions, and rounds only the number you see.
Is what I enter in this converter saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Is this converter free to use?
Yes. It is free, needs no sign-up and has no usage limit.
Last reviewed: October 3, 2026