Weight Converter

A pound is exactly 453.59237 grams, which fixes the ounce at 28.349523125 g and the stone at 14 pounds. The tonne here is the metric one, 1000 kg — not the US short ton or the UK long ton. Pick your two units and the value passes through grams.

Seven units make 42 directed pairs, but the converter stores only seven numbers: what each unit is worth in kilograms. Every conversion runs through that pivot — multiply by the factor of the unit you have, divide by the factor of the unit you want — so there is one rate per unit to keep right instead of 42, and none of them can drift out of step with the rest. The factors are settled by definition rather than by weighing anything. The pound is fixed at exactly 0.45359237 kilograms; the ounce is a sixteenth of it, exactly 28.349523125 g, and the stone is fourteen pounds, exactly 6350.29318 g. The metric side is exact by construction too. So 1 kg = 2.2046226218 lb is not a measurement carrying error bars — the only imprecision you see is the six decimal places on screen. The trap in this family is the word ton, which in English names three different masses: the metric tonne of 1000 kg, the US short ton of 907.18474 kg and the UK long ton of 1016.0469088 kg. Only the metric tonne is offered here, and t means that one; a short-ton figure copied in unchecked is about 9 % light. One more distinction: what is converted is mass, the amount of matter, not gravitational weight, which is a force and depends on where you stand. On Earth's surface the two match for everyday purposes.