Weight converter.

Convert between kilograms, pounds, stone, ounces, grams, tonnes, and more. Metric and imperial. Exact values, no rounding.

✓ Free 🌍 International

Weight Converter

Convert any weight or mass.

Unit system

Value

From

Result

Helpful tips

⚖️

Stone is a UK-only unit

Used almost exclusively in Britain and Ireland for body weight. Most of the world uses kilograms — don't assume your audience knows what stone means.

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Two very different tons

A US short ton is 2,000 lb (907 kg). A UK long ton is 2,240 lb (1,016 kg). A metric tonne is 1,000 kg exactly. They are not interchangeable — always check which is meant.

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Medicine uses mg and µg

Milligrams and micrograms are standard in pharmacology. One microgram is one-millionth of a gram. Precision here matters — a small error can have serious consequences.

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Shipping quotes in kilograms

International freight and postal systems almost universally use kilograms, not pounds. Convert before you book to avoid unexpected surcharges.

How weight conversion works

One base unit, every
other unit derived from it

Every weight conversion follows the same logic: convert the input to kilograms, then convert from kilograms to the target unit. Because every unit has a fixed, exact relationship with the kilogram, there is no approximation involved — the result is always perfectly precise.

The metric system scales by powers of ten. A tonne is exactly 1,000 kilograms; a gram is exactly 0.001 kilograms; a milligram is a thousandth of that. Imperial units have been defined in metric terms since 1959, when the International Yard and Pound Agreement fixed one pound as exactly 453.59237 grams. Everything else — ounces, stone, tons — cascades from that single defined value.

The main source of confusion is that "ton" means different things depending on where you are. A US short ton is 2,000 pounds. A UK long ton is 2,240 pounds. A metric tonne is 1,000 kilograms (about 2,204.6 pounds). All three appear in everyday use in different industries and regions.

Method value × from_kg ÷ to_kg

Imperial 1 lb = 453.59237 g exactly

Metric 1 t = 1,000 kg · 1 g = 0.001 kg

FAQ

Common questions

Strictly speaking, mass is the amount of matter in an object, measured in kilograms. Weight is the force that gravity exerts on that mass, measured in newtons. A 70 kg person has the same mass on Earth and the Moon, but weighs about six times less on the Moon because gravity is weaker there. In everyday life, and throughout this converter, "weight" and "mass" are used interchangeably because we are almost always working at the surface of the Earth where the distinction has no practical effect.

Stone has been used in Britain for centuries, originally because a stone was a convenient unit for weighing livestock at market. Its value was standardised at 14 pounds in the 14th century. When the UK adopted the metric system for most official purposes, body weight was one of the cultural exceptions that stuck, alongside road distances in miles and draught beer in pints. Today stone is used almost exclusively in the UK and Ireland for personal body weight, and rarely anywhere else in the world. Most UK bathroom scales show both stone/pounds and kilograms.

There are three distinct units that all go by the name "ton." The metric tonne (sometimes spelled "tonne" to distinguish it) is exactly 1,000 kilograms, or about 2,204.6 pounds. The US short ton is 2,000 pounds, or about 907 kilograms. The UK long ton is 2,240 pounds, or about 1,016 kilograms. In the US, "ton" typically means the short ton. In the UK, "ton" historically referred to the long ton, though metric tonnes are now standard in most commercial contexts. In international shipping and trade, metric tonnes are the norm.

To express a weight as "X stone Y pounds," first convert kilograms to total pounds by multiplying by 2.204623. Then divide by 14 to get the number of whole stone, and the remainder is the leftover pounds. For example, 75 kg is 165.35 pounds total. Divide by 14 to get 11 stone remainder 11.35 pounds — so 75 kg is approximately 11 stone 11 pounds. The converter on this page shows the stone value as a decimal. To split it into stone and pounds, take the decimal portion and multiply by 14.

For dry goods and postal weights, yes — an ounce is always the avoirdupois ounce, exactly 28.349523 grams, with 16 ounces to a pound. However, recipes occasionally use a different unit: the fluid ounce, which measures volume, not mass. A fluid ounce of water happens to weigh close to one ounce, but this does not hold for other liquids. There is also a third unit, the troy ounce (31.1035 grams), used exclusively for precious metals like gold and silver. This converter uses avoirdupois ounces throughout.

All conversions use exact, internationally defined values. The kilogram-to-pound relationship is fixed by treaty at exactly 0.45359237 kg per pound, with no rounding. All other units cascade from that. The only limitation is the floating-point precision of the browser's JavaScript engine, which is accurate to roughly 15 significant digits — far beyond anything needed in practice. Results are displayed to up to 8 significant figures. For pharmaceutical or laboratory work at very small scales (micrograms and below), a dedicated scientific calculator would be more appropriate.