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Convert between metric and imperial weights with exact factors.
Convert weights and masses between milligrams, grams, kilograms, ounces, pounds, and metric tons. Uses the exact international pound (0.45359237 kg), so results match official conversion tables.
Weight conversion lives at the intersection of cooking, fitness, shipping, and science — and it has more unit traps than any other quantity. The metric side is clean: milligrams, grams, kilograms, and metric tonnes (1,000 kg), all decimal. The imperial side is a historical attic: ounces, pounds, stones (14 pounds, still used for body weight in Britain and Ireland), and no fewer than three different 'tons' — the U.S. short ton of 2,000 lb, the metric tonne of 1,000 kg, and the British long ton of 2,240 lb. A 'ton' without qualification is genuinely ambiguous, which is why freight contracts specify which one.
The conversion factors are exact by international agreement: one pound equals 0.45359237 kilograms, one ounce equals 28.349523125 grams, and one stone equals 6.35029318 kilograms. In the other direction, one kilogram equals 2.20462 pounds and one gram equals 0.035274 ounces. For everyday estimating, 1 kg is about 2.2 lb and 1 oz is about 28 g; for trade, medicine, or engineering, use the full-precision factors. A pedantic but useful note: physicists distinguish mass (kilograms) from weight (a force, properly measured in newtons), but every scale, recipe, and shipping label on earth uses 'weight' to mean mass, and so does this calculator.
Context decides which units to reach for. Recipes: grams in most of the world, ounces and cups in the U.S. Body weight: kilograms nearly everywhere, pounds in the U.S., stones and pounds in the UK. Parcels: airline limits are set in kilograms (typically 23 kg for checked bags, about 50.7 lb). Precious metals: the troy ounce (31.1035 g), which is about 10 percent heavier than the avoirdupois ounce used for everything else — a classic trap for the unwary gold buyer.
Every unit converts through grams with its exact factor: 1 ounce = 28.349523125 g, 1 pound = 453.59237 g, 1 metric ton = 1,000,000 g. The result is value × factor[from] ÷ factor[to].
Multiply by 2.20462 lb per kg: 2.5 x 2.20462 = 5.51155, rounded to 5.51 lb. For a recipe, 'about five and a half pounds' is the honest phrasing. Reverse: 5.51 lb x 0.45359237 = 2.4995 kg, confirming the round trip within rounding. This is the everyday workhorse conversion for shoppers comparing a European recipe's 500 g bag against an American 1 lb bag: 500 g is 1.102 lb, so the European bag holds about 10 percent more — worth knowing when a recipe calls for 'one bag.'
One stone is exactly 14 pounds, so 10 stone is 140 lb. Multiply by 0.45359237: 140 x 0.45359237 = 63.5029, rounded to 63.5 kg. Equivalently, 10 x 6.35029318 = 63.5029 kg directly. A UK bathroom scale reading '10 st 7 lb' converts as 147 lb x 0.45359237 = 66.68 kg. The stone persists because people like human-scale numbers — saying '11 stone' feels more natural than '69.85 kilograms' — but every official form wants kilograms, making this one of the most-searched conversions in Britain.
About 2.20462 lb. The exact factor is 1 kg = 2.20462262185 lb.
16 ounces. Enter 16, choose oz → lb, and you get exactly 1 — the avoirdupois ounce is defined as 1/16 of a pound.
These are the avoirdupois ounces and pounds used in everyday and commercial weighing — the same system as US and UK food labels and bathroom scales.