Unit converter
Convert length, weight, temperature, volume, speed and more between metric and imperial — instantly.
Runs 100% in your browserHow to convert units
- Pick a category. Choose length, mass, temperature and so on.
- Choose units. Select the from and to units.
- Type a value. The converted result updates live; click Copy for full precision.
How the conversions are calculated
Most conversions are a single ratio against a base unit — metres for length, grams for mass, litres for volume. Each unit stores how big it is in that base (a foot is 0.3048 m, a pound is 0.45359237 kg), so the tool just multiplies into the base and divides back out. Many of these ratios are exact by definition rather than approximate: an inch is precisely 25.4 mm and a pound is precisely 0.45359237 kg, so the only rounding you see is on the display — copy the result for full precision.
Why temperature is the exception
You can't convert temperatures by multiplying, because their scales don't share a zero point: 0 °C is freezing water, 0 °F is much colder, and 0 K is absolute zero. Going from Celsius to Fahrenheit needs both a factor and an offset (×9/5, then +32); Kelvin is Celsius shifted by 273.15. This converter applies those proper formulas, so 20 °C correctly becomes 68 °F rather than a meaningless scaled number.
The gallon trap, and KB vs KiB
A couple of unit families hide real ambiguity, so both forms are listed explicitly. The US gallon (3.785 L) is about 17% smaller than the UK/imperial gallon (4.546 L) — the same word, two volumes — and US cups, pints and quarts differ from imperial ones too, which is why a recipe converted with the wrong gallon goes wrong. Digital storage has the same split: a kilobyte is 1,000 bytes (decimal, how drives are sold) while a kibibyte is 1,024 (binary, how RAM and many OSes count). Pick the member that matches your source and the result is unambiguous.
Private and offline
It's all pure client-side arithmetic — no network calls — so it keeps working with no connection and uploads nothing. For aspect-ratio math on images and video, the aspect ratio calculator is the specialised tool.
Frequently asked questions
- Length, mass/weight, temperature, volume, area, speed, digital storage and time — each with the common metric and imperial units.
- Conversions use exact ratios where they exist (e.g. 1 inch = 25.4 mm) and double-precision arithmetic, with sensible rounding on display. You can copy the full-precision result.
- Temperature is not a simple ratio, so Celsius, Fahrenheit and Kelvin are converted with their proper offset formulas, not multiplication.
- Yes — it is pure client-side math with no network calls, so it keeps working with no connection and uploads nothing.