Weight Converter

Weight Converter moves between the metric and imperial systems and within each of them. Kilograms, grams, pounds and ounces cover most needs; stones, tonnes and both kinds of ton are there for the cases where they do not.

A pound is exactly 0.45359237 kilograms, agreed internationally in 1959, which makes every imperial weight conversion exact rather than approximate. The familiar 2.2 pounds per kilogram is a rounding of 2.20462, and over a few hundred kilograms the difference becomes visible.

Two traps are worth naming. A US ton is 2,000 pounds, about 907 kg, while a UK long ton is 2,240 pounds, about 1,016 kg, and a metric tonne is 1,000 kg exactly -- three different things called roughly the same word. And an ounce of weight is not a fluid ounce of volume; they are unrelated units that share a name.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

• Shows result, to twelve digits, conversion factor, the other way and in scientific notation together, so you are not running it twice
• A results table you can read across
• Updates as you type, with no button to press and no page reload
• Copy the result in one click
• Free, no sign-up, and it runs entirely in your browser

The weight converter is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

• Converting body weight between kilograms and pounds
• Reading a recipe in ounces when your scale is metric
• Converting stones and pounds into kilograms
• Checking a shipping weight in tonnes against tons