About Measurement Units
We build free unit converters and plain-English reference guides for the measurement questions people actually run into: a recipe in cups, a European shoe size, a tyre pressure quoted in bar, a drive that says 1 TB but reads 931 GB.
What this site is for
Most people arrive with one specific question rather than a general interest in metrology, so the site is organised around those questions. Each category has its own converter, a reference table, the formula behind it, and a short explanation of why the units are the way they are. If you only need a number, the converter is the first thing on every page. If you want to understand the number, the explanation sits underneath it.
Where our numbers come from
Every conversion factor is taken from published reference values from the National Institute of Standards and Technology (NIST) and the International Bureau of Weights and Measures (BIPM). Several of the factors we use are exact by definition rather than measured approximations: an inch is exactly 2.54 centimetres, and a mile is exactly 1,609.344 metres. We calculate with the exact value and round only the result.
Where a unit genuinely differs by region we list both rather than averaging them. A US gallon is 3.785 litres and a UK gallon is 4.546 litres, roughly 20 per cent apart, so a converter offering a single unlabelled “gallon” is really offering you a coin toss.
How the converters work
They run entirely in your browser. The numbers you type are converted on your own device and are never sent to our server, stored, or logged. There is no account to create and nothing to install.
Where we are deliberately careful
- Cooking weights are typical values. A cup of flour can vary by ten per cent or more depending on the brand and how tightly it is packed. We give a sensible working figure, not a guarantee.
- Clothing and shoe sizes are convention, not physics. They are not built on a physical unit and they vary between brands. Our charts are a starting point; the brand size guide wins.
- Critical uses need a second source. For medicine dosing, engineering tolerances, and legal or commercial measurement, verify against an authoritative reference before relying on a figure from any website, including this one.
Corrections
If you spot an error, or there is a conversion pair you would like added, please get in touch. A correction to a published factor is the most useful message we can receive, and every category page carries the date it was last reviewed.