Weight converter

One kilogram is 2.20462262 pounds, and one pound is exactly 0.45359237 kilograms. The pound figure is a definition set by the 1959 international yard and pound agreement, not a measurement, so every kilogram-to-pound conversion is exact rather than approximate. For rough mental arithmetic, doubling and adding ten percent is accurate to within half a percent.

Multiply the kilograms by 2.20462 to get total pounds, then divide by 14 for whole stone and keep the remainder in pounds. For 70 kg: 70 × 2.20462 = 154.32 lb, and 154.32 ÷ 14 gives 11 stone with 0.32 lb remaining. The stone remains in everyday use for body weight in the United Kingdom and Ireland.

A metric tonne is exactly 1,000 kilograms, about 2,204.6 pounds. A US short ton is 2,000 pounds, about 907.2 kilograms. A UK long ton is 2,240 pounds, about 1,016 kilograms. The three differ by up to twelve percent, so shipping and freight documents must state which is meant.

Until 2019 the kilogram was defined by a platinum-iridium cylinder held near Paris, and that artefact had drifted by roughly 50 micrograms relative to its official copies. The 2019 redefinition fixed the Planck constant at exactly 6.62607015 × 10⁻³⁴ joule-seconds, allowing the kilogram to be realised from physical constants in any suitably equipped laboratory.

A troy ounce is 31.1034768 grams and is used for precious metals. An avoirdupois ounce, the everyday ounce, is 28.349523125 grams. A troy ounce is therefore about 10% heavier. Gold and silver prices are always quoted per troy ounce, which is why converting a bullion weight with the everyday factor understates its value.

Not in physics. Mass is the amount of matter in an object and does not change with location. Weight is the force gravity exerts on that mass, measured in newtons, and varies with local gravity — an object weighs about one sixth as much on the Moon. Everyday usage treats the two as interchangeable because terrestrial gravity barely varies.