Unit Converter
How to use
Converts values between units of length, weight, temperature, area, volume and speed. Pick a category, choose the units you are converting between, and the result updates as you type.
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- Converting a recipe's measurements between metric and imperial units
- Checking a shipping package's weight or dimensions against a carrier's unit requirements
- Converting a temperature reading between Celsius and Fahrenheit while traveling
- Translating a product spec sheet between unit systems for an international audience
Exact conversions, defined conversions, and the ones that are neither
Some conversions carry no error whatsoever because the relationship is a definition rather than a measurement. An inch has been exactly 25.4 millimetres since the international yard and pound agreement of 1959; a pound is exactly 0.45359237 kilograms by the same agreement. Those are not approximations that happen to be very good: they are exact by fiat, and any rounding you see is your own, not the conversion's. Temperature between Celsius and Fahrenheit is likewise exact, since both scales are now defined against the kelvin.
Other conversions look identical in the interface and are not the same kind of thing. A nautical mile is exactly 1,852 metres by definition, but the survey foot used in older US land records differs from the international foot by two parts per million: invisible on a room measurement and significant across a county boundary. Fluid measures are worse: a US fluid ounce and an imperial fluid ounce differ by about four percent, and a US gallon and an imperial gallon by about twenty. A recipe or a fuel figure converted with the wrong one is wrong by an amount large enough to matter.
Weight and mass are the distinction people most often collapse. A kilogram is a mass and a pound-force is a force, and converting between them silently assumes standard Earth gravity. For everyday use that assumption is fine and universal. For engineering work it is the assumption that has to be stated, because it is the one that stops being true the moment anything accelerates. Where this tool converts between units in different physical dimensions, it is applying a convention rather than a mathematical identity, and it is worth knowing which of the two you are relying on.
Free and private. Everything runs on your own device, with no account and no uploads.
Converting between metric and imperial units for length, weight, temperature, area, volume or speed is a constant small annoyance. This tool handles them all, updating as you type.
Conversions use standard, precise conversion factors, so results are accurate to many decimal places.
Yes, temperature uses a different formula internally (not a simple multiplier) but works the same way from your side, just pick your units.
A wide range of common and several less common units are included per category; check the dropdown list for your specific unit.
Both, labelled separately, because they differ by about 20%. Gallons (US) is 3.785 litres and Gallons (UK) is 4.546 litres, and pints come in both versions too. Cups and fluid ounces are the US measures, as most recipes online use them.
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Pick a category
Choose length, weight, temperature, area, volume or speed.
- 2
Choose the units
Select which units you are converting between.
- 3
Read the result
The converted value updates as you type.
- ·Double-check whether a "ton" is metric, US short, or UK long, they differ and it's a common source of errors.
- ·For area and volume conversions, watch the exponent, converting length units directly won't give you the right area factor.
- ·Round results only at the end of a calculation chain to avoid compounding small rounding errors.