Convert weight between milligrams, grams, kilograms, tonnes, ounces, pounds and stone, with a full conversion table for every unit. Free, in your browser.
How the weight converter works
All conversions go through the kilogram, the SI base unit of mass: your value is multiplied into kilograms, then divided by the target unit's size. The avoirdupois pound has been defined as exactly 0.45359237 kg since 1959, the ounce is one sixteenth of that pound, and the stone — still used for body weight in the UK and Ireland — is exactly 14 pounds (6.35029318 kg). The tonne (metric ton) is exactly 1,000 kg. Because every factor is an exact definition, converting back and forth loses nothing beyond display rounding.
kg = value × from.toBase → result = kg ÷ to.toBase // 1 lb = 0.45359237 kgFrequently asked questions
Is anything I enter uploaded anywhere?
No. Everything runs locally in your browser — nothing you enter is sent to a server, logged or stored. Only the value and selected units appear in the URL so you can bookmark or share a specific conversion.
How many kilograms is a pound, exactly?
Exactly 0.45359237 kg — that has been the international definition of the avoirdupois pound since 1959. Going the other way, one kilogram is about 2.20462 pounds. The quick mental shortcut of 'multiply kg by 2.2' is accurate to within 0.2%.
What is a stone?
A stone is 14 pounds, or exactly 6.35029318 kg. It survives mainly for body weight in the UK and Ireland — someone who is '11 stone 4' weighs 11 × 14 + 4 = 158 pounds, about 71.7 kg. This tool converts whole stones; convert the leftover pounds separately.
Last updated: 8 July 2026
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