Unit Converter
Eleven categories, a hundred-plus units, instant conversion.
Runs entirely in your browser
Loading the tool…
Same value in every unit
Every category converts through its SI base unit rather than through a table of pairs, so kilometres to miles and miles to kilometres are the same arithmetic run in opposite directions and a value survives a round trip unchanged. Converting between categories, kilograms to metres, is refused rather than quietly answered with a number that means nothing.
The awkward cases are the ones worth checking a converter on. Temperature is not a simple ratio, because the scales have different zero points, so a conversion has an offset as well as a factor, Rankine included. The US gallon and the imperial gallon differ by about a fifth, which turns a recipe into a mess. And a kilobyte is either a thousand bytes or 1024 depending on who is counting, which is why the units are listed separately here instead of being averaged into a wrong answer.
For a whole chart rather than a single answer, conversion tables generates the range and prints it. For arithmetic on the result, the calculator takes a full expression.
How to use it
- Choose a category such as Length or Temperature.
- Pick the unit you have and the unit you want.
- Type the value. The result updates as you type, and one button swaps the pair.
Questions
Are KB and KiB the same?
No. A kilobyte is 1000 bytes and a kibibyte is 1024. Storage manufacturers use the first, operating systems often use the second, which is why a '1 TB' drive shows as 931 GB. Both are in the list.
Why will it not convert kilograms to litres?
Because that conversion needs to know what the substance is. A litre of water is about a kilogram, a litre of oil is nearer nine hundred grams, and a litre of lead is over eleven kilograms. A converter that answered would be guessing, so it says no instead.
Which gallon, pint and ounce are these?
Both, listed separately. US and imperial gallons differ by about twenty per cent and their pints differ too, so they are never the same unit with two names. A fluid ounce is a volume and an ounce is a weight, which is the other trap; they are in different categories here.
How exact are the answers?
Exact to the limits of double precision arithmetic, which is about fifteen significant digits, using the internationally defined factors: an inch is exactly 25.4 millimetres, a pound is exactly 0.45359237 kilograms. Where a factor is defined rather than measured, the result is as exact as the definition. Up to ten significant digits are shown, because the ones past that are rounding dust rather than information.
Are kilobytes 1000 or 1024 bytes?
Both exist and both are here. A kilobyte in the SI sense is 1000 bytes, which is what disk manufacturers use; a kibibyte is 1024, which is what operating systems usually count in. That difference is why a 500 GB drive shows as about 465 GB once it is formatted.
Your data stays on your device
Everything above runs inside your browser as WebAssembly compiled from Rust. Nothing you type is uploaded, logged or stored on a server. You can load this page once, go offline, and it still works.
This page makes no requests at all, to anywhere. That is not a promise in the copy: it is a Content-Security-Policy header your browser enforces, and connect-src on it is none. Open the network tab and watch nothing happen.