Unit Converters
Eight converters using exact, internationally defined factors — metric to imperial and back, with the full equation shown every time.
Most conversions are exact — a few are not
An inch is exactly 25.4 millimetres. A pound is exactly 0.45359237 kilograms. A mile is exactly 1,609.344 metres. These are definitions, agreed internationally, not measurements — so the Length Converter and Weight Converter can be precise to as many decimal places as you need. Temperature is the odd one out: the Celsius and Fahrenheit scales have different zero points as well as different step sizes, which is why the Temperature uses an offset as well as a ratio.
Area and volume scale by squares and cubes
This is where intuition fails most often. If a length doubles, the area quadruples and the volume goes up eight times. So converting square metres to square feet uses the length factor squared (3.2808² ≈ 10.764), and cubic metres to cubic feet uses it cubed (≈ 35.315). The Area Converter and Volume Converter handle this automatically — but knowing why the numbers look unfamiliar makes it much easier to spot when a figure is wrong by a factor of ten.
Speed, data and the definitions that vary
The Speed Converter covers km/h, mph, m/s and knots — a knot being one nautical mile per hour, where a nautical mile is exactly 1,852 metres. The Data Storage handles the messiest case on the site: a kilobyte is 1,000 bytes under the SI definition but 1,024 under the binary convention that operating systems still use, which is why a "500 GB" drive shows as roughly 465 GB in Windows. The converter lets you pick which convention you mean.
Convert before you calculate, not during
The most reliable habit in any multi-step calculation is to convert everything into one system at the start and work in that system throughout. Mixed units mid-calculation are how a Mars orbiter was lost in 1999, and how kitchen and building projects go wrong far more often. If you need several unit types at once, the Unit Converter has them all in one place.