Weight & Mass Converter
The pound is defined as exactly 0.45359237 kilograms, so every conversion here is exact rather than approximate. Stones are shown in the British stone-and-pounds format people actually use.
Value to Convert
Troy ounces are included for precious metals — they are heavier than ordinary ounces.
All units
The same quantity expressed every other way.
The pound is defined in kilograms, not the other way round
Since 1959 the international avoirdupois pound has been defined as exactly 0.45359237 kilograms. That means the imperial system is now formally anchored to the metric one: every ounce, stone and ton is derived from that single exact figure. It also means conversions never need to be approximate — 0.45359237 is not a measurement, it is a definition.
Troy ounces are a different unit entirely
A troy ounce is 31.1034768 grams; an ordinary avoirdupois ounce is 28.349523125 grams. Gold, silver and platinum are priced per troy ounce, so treating a gold quote as ordinary ounces overstates the quantity by about ten percent. This is a genuinely expensive mistake and it happens constantly, which is why troy ounces are listed separately here rather than hidden in a dropdown of near-identical names.
Short tons, long tons and tonnes
Three units share almost the same name and none of them are equal. A metric tonne is 1000 kilograms. A US short ton is 2000 pounds, about 907 kilograms. A British long ton is 2240 pounds, about 1016 kilograms. Shipping documents, freight quotes and commodity contracts all use different ones, and the gap between the largest and smallest is over ten percent.
Mass versus weight
Strictly, kilograms measure mass and newtons measure weight — the force gravity exerts on that mass. In everyday use the words are interchangeable because gravity is effectively constant across the Earth's surface. The distinction only becomes practical in physics problems and in aerospace, where local gravity varies enough to matter.