Unit Converter
A conversion table is easy to write and easy to get subtly wrong, and the mistakes are the ones nobody notices: a pint that turns out to be the American one, a ton that is the short ton, a factor rounded to four figures so the answer comes back a little short. Every factor here is the exact defined value — an inch is 25.4 millimetres by definition, a pound is 0.45359237 kilograms — and the table is checked against published figures before any answer is shown.
What this generator does
Converts your amount through the family's base unit and shows it in every other unit of that kind at the same time, so the answer can be read in context rather than one pair at a time.
How to use this tool
- Choose what you are converting.
- Enter the amount and pick the units either side.
- Read the answer, and the same amount in every other unit of that kind.
- Note that UK and US pints, gallons and fluid ounces are listed separately.
Understanding the controls
- What are you converting
- Length, weight, volume, area, speed, time, data or temperature. Units only convert within their own kind, which is why they are grouped.
- Amount and units
- The figure you have and the units either way. UK and US pints, gallons and fluid ounces are separate entries, since they are different measures with the same name.
Common use cases
- Converting a recipe between metric and imperial
- Working in feet and inches from a metric drawing
- Checking a speed, a distance or a weight quoted in other units
- Converting file sizes between the 1000 and 1024 kinds of megabyte
- Reading a temperature in the other scale
How this generator works
Two checks run before an answer appears. Every unit in the family is converted and converted back, and must return the figure it started from. Then a list of published exact conversions is worked out again — an inch as 25.4 millimetres, an acre as 4,840 square yards, a knot as 1.852 kilometres an hour, minus forty as the point where the two temperature scales meet — and each must come out right to the last figure. Temperature is handled apart from the rest, because it is a scale with an offset rather than a simple multiple: doubling the number does not double the temperature.
Randomness and fairness
Nothing is random. The factors are fixed definitions, so the same amount always converts the same way.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Units convert within their own kind only. Turning a volume into a weight needs a density, which depends on what the substance is.
- Figures are rounded for display; the arithmetic behind them keeps full precision.
- Some units carry the same name in different systems, and only the UK and US versions are separated here.
- Historic and regional measures are not included.
Privacy and your data
Conversions run in your browser. Nothing you enter is transmitted or stored.
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