Weight and Mass converter

Every unit on this page is referenced to the kilogram, the SI base unit of mass. A gram is 0.001 kg, a metric ton is 1,000 kg, and the imperial and US customary units slot in at their own fixed ratios — a pound is defined as exactly 0.45359237 kg, and an ounce as 0.028349523125 kg (one sixteenth of a pound).

The most-used pair here is kilogram to pound. Multiply by 2.204622622 to go from kilogram to pound:

lb = kg × 2.204622622

Reverse it by multiplying by 0.45359237, the same as dividing by 2.204622622. A 75 kg adult weighs 75 × 2.204622622 = 165.35 lb, and a 16-ounce package weighs 16 × 28.349523125 g = 453.59 g — which, not coincidentally, is exactly how many grams are in one avoirdupois pound.

These units show up in very different corners of daily life. Cooking in the US still leans on ounces and pounds while most of the rest of the world bakes by grams and kilograms, which is why so many recipes need converting before they're usable. Shipping carriers price parcels by weight bands in kilograms internationally and pounds domestically in the US. Gyms and medical charts track body weight in whichever unit the country's health system standardized on. Precious metals and gemstones are a world of their own: gold and silver are priced in troy ounces, diamonds in carats, and both are deliberately kept separate from everyday grocery-scale units.

The single biggest point of confusion is that “ounce” means two different things depending on context. An avoirdupois ounce (the one on a kitchen scale) is 28.349523125 g, but a troy ounce (used for gold, silver, and other precious metals) is 31.1034768 g — about 10% heavier. Quoting a gold price in the wrong kind of ounce produces a meaningfully wrong number, not just a rounding error. Short tons (US, 907.18 kg), long tons (UK, 1,016.05 kg), and metric tons (1,000 kg) are a second common trap, since all three are casually called “a ton” but differ by up to 12%.