Weight Converter
Kilograms, pounds, ounces, stones and tonnes, converted both ways.
Body weight in stones, recipe quantities in ounces, shipping in kilograms, freight in tonnes that mean different things in different countries — weight carries more conflicting conventions than any other everyday measurement. This converter covers nine of them with exact factors, and shows all nine at once so a figure can be checked at a glance.
| Unit | Symbol | Value |
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How it works
Choose the units
Metric, imperial, and both kinds of ton.
Enter the amount
Conversion and factor appear immediately.
Compare all nine
The reference table shows the same weight in every unit.
Mass, weight, and why the distinction rarely matters here
Strictly, a kilogram measures mass — how much matter something contains — while weight is the force gravity exerts on that mass, properly measured in newtons. The same object has the same mass on the Moon and one sixth the weight. Every unit on this page is a mass unit, so the conversions hold anywhere in the universe.
In practice the two words are used interchangeably because everyone lives at the same gravitational field strength, give or take a fraction of a percent. That fraction is measurable: you weigh about 0.5% less at the equator than at the poles, partly from Earth’s bulge and partly from its rotation. Scales calibrated for one latitude read slightly wrong at another, which is why trade-approved scales are calibrated on site.
The pound is the one unit where the ambiguity is built into the name. The pound-mass used here is defined as exactly 0.45359237 kilograms; the pound-force is the weight of that mass under standard gravity. Outside engineering the distinction is almost never made, and when someone gives a weight in pounds they mean the mass unit.
Ounces, tons and the units that mean two different things
The ounce has two forms still in daily use. The avoirdupois ounce, at 28.35 grams, is the one in every recipe and on every food label. The troy ounce, used exclusively for precious metals, is 31.10 grams — about 10% heavier. A "one ounce" gold coin therefore weighs more than an ounce of anything else, which is a genuine source of confusion in pricing rather than a curiosity.
Ton is worse, because there are three. The metric tonne is 1000 kg. The US short ton is 2000 pounds, about 907 kg. The UK long ton is 2240 pounds, about 1016 kg. A shipping quote in "tons" can differ by 12% depending on which was meant, so this converter names all three explicitly rather than offering a generic "ton".
The stone survives only in Britain and Ireland, and only for body weight: 14 pounds, about 6.35 kg. It never appears on packaging or in medicine, which means a weight given in stones almost always has to be converted before it can be used for anything — a dosage calculation, a BMI, a piece of gym equipment.