Convert between metric and imperial units across seven categories: length, weight, temperature, volume, data, speed, and area.
How to use this tool
- Pick a category.
- Enter an amount and choose the units.
- The result appears instantly — use the ⇄ button to reverse the conversion.
Notes on accuracy
Conversion factors here are the exact internationally defined values where they exist:
- 1 inch = exactly 25.4 mm
- 1 pound = exactly 0.45359237 kg
- 1 mile = exactly 1609.344 m
Temperature is not a simple ratio — it needs an offset as well as a scale — so it is converted through Celsius rather than a multiplication factor.
The units people get wrong
US and UK gallons are different. A US gallon is 3.785 litres; a UK (imperial) gallon is 4.546 litres — about 20% larger. Both are listed separately. The same applies to pints. US cups, teaspoons, and tablespoons are also listed explicitly, since metric and Australian equivalents differ.
Kilobytes are ambiguous. Storage manufacturers use 1 KB = 1000 bytes; operating systems traditionally use 1024. Both are listed: KB/MB/GB for the decimal (1000-based) values and KiB/MiB/GiB for the binary (1024-based) ones. This is why a "1 TB" drive shows as about 931 GB in Windows — nothing is missing, the two are just counting differently.
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FAQ
Is anything sent to a server?
No. All conversions are arithmetic performed in your browser.
How accurate are the results?
Results are computed at full double precision and displayed to ten significant figures. For any everyday purpose the answer is exact.
Why is my "1 TB" hard drive smaller than 1 TB?
It is not. The manufacturer counts 1 TB as 1,000,000,000,000 bytes; Windows displays that same number as 931 GiB because it divides by 1024 three times. Compare TB with TB, or use the TiB row here.
What is the difference between mass and weight?
Strictly, mass is the amount of matter and weight is a force. In everyday use kilograms and pounds are used for both, and this converter follows that convention.
Can I convert fuel economy, mpg to L/100km?
Not currently — that is an inverse relationship rather than a simple ratio, so it needs its own handling. Length, volume, and the other seven categories cover most needs.
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