About the Weight Converter
This weight converter handles the eight units people actually meet in daily life: milligrams, grams, kilograms and tonnes on the metric side, and ounces, pounds, stones and US short tons on the imperial and customary side. Conversions run through the kilogram using the exact 1959 definition of the pound, so kilograms to pounds is not an approximation. The table beneath the result shows your figure in all eight units at once, which is particularly handy for recipes, shipping weights and body weight, where three different units can appear on the same page.
How to use the Weight Converter
- 1
Enter the figure you want converted in the Value field.
- 2
Pick the unit it is measured in from the From list.
- 3
Pick your target unit from the To list.
- 4
Check the conversion details panel for the single-unit factor, and the full table for every other unit.
What people use it for
Body weight across systems
British clinics often record weight in kilograms while people think in stones. 11 st 4 lb is 158 lb, which is 71.67 kg — convert to pounds first, then to kilograms.
Baking from an American recipe
US recipes give butter and flour in ounces or pounds. Eight ounces of flour is 226.8 g, which matters far more in baking than it does in a stew.
Shipping and freight quotes
Carriers quote in kilograms, pounds or tons depending on the market, and the two tons differ by around ten percent, so confirming which one is meant avoids a costly surprise.
The kilogram after 2019
Until May 2019 the kilogram was the last SI base unit still defined by a physical object: a platinum-iridium cylinder cast in 1889 and stored under three nested bell jars near Paris, known as the International Prototype of the Kilogram. Its official copies, distributed to national laboratories, drifted relative to it by something on the order of fifty micrograms over a century, and nobody could say which had changed. Since the 2019 redefinition, the kilogram is instead fixed by giving the Planck constant the exact value 6.62607015 × 10⁻³⁴ joule seconds. Combined with the already-fixed definitions of the second and the metre, that pins the kilogram to nature rather than to a lump of metal, and it is realised in practice using a Kibble balance, which balances mechanical against electromagnetic power. Nothing changed at the everyday scale — a kilogram of flour is still a kilogram of flour — but the unit is now stable to a level no artefact could match.
Pounds, stones, tonnes and the two different tons
The avoirdupois pound has been exactly 0.45359237 kilograms since the 1959 International Yard and Pound Agreement, which makes one kilogram 2.2046226 pounds. The ounce is a sixteenth of a pound, exactly 28.349523125 grams. The stone, still widely used for body weight in the UK and Ireland, is 14 pounds or about 6.35 kilograms; it was abolished for trade in the UK in 1985 but survives socially. Confusion is most expensive at the top of the scale, where three different tons circulate. The metric tonne is 1,000 kg, about 2,204.6 lb. The US short ton is 2,000 lb, about 907.18 kg. The imperial long ton, not offered here, is 2,240 lb or about 1,016 kg. A shipment quoted in short tons is roughly ten percent lighter than the same number of tonnes. One further trap sits in jewellery and bullion: precious metals are weighed in troy ounces of 31.1035 g, which is about ten percent heavier than the 28.35 g avoirdupois ounce used here, so this converter should not be used for gold or silver pricing.
Tips
- Multiplying kilograms by 2.2 is accurate to within a quarter of a percent, which is fine for luggage but not for dosing or trade.
- Convert stones and pounds into total pounds before entering them, since the two parts cannot be entered together.
- Recipes are far more forgiving of volume errors than weight errors — where a recipe gives grams, weigh rather than scoop.