Converters
Convert between pounds, kilograms, ounces, grams, and stones — enter a weight in one unit and see it in all five, including the stones-and-pounds form common in the UK.
Everything converts through kilograms using exact definitions. Since 1959 the international pound has been defined as exactly 0.45359237 kg, so 1 lb = 0.45359237 kg with no rounding in the definition itself. The rest follow: 1 oz = 1/16 lb = 0.028349523125 kg, 1 g = 0.001 kg, and 1 stone = 14 lb = 6.35029318 kg.
About stones: a stone is exactly 14 pounds. It is the everyday unit for body weight in the UK and Ireland, where people give their weight as stones and pounds together — "11 st 4 lb" means 11 × 14 + 4 = 158 lb (about 71.7 kg). Stones are rarely used in the US, which is why both the plain decimal value and the stones-and-pounds breakdown are shown above.
Worked example: 180 lb × 0.45359237 = 81.6466 kg. In ounces that is 180 × 16 = 2,880 oz, in grams about 81,646.63 g, and in stones 180 ÷ 14 = 12.857 st — written the UK way, 12 st 12 lb.
How many kilograms is 150 pounds? 150 × 0.45359237 = 68.04 kg. For a rough mental conversion, halve the pounds and subtract a tenth of that result: 150 → 75 − 7.5 = 67.5 kg — close, but the converter above is exact.
Is a US ounce the same as a UK ounce? For weight, yes — both use the international avoirdupois ounce of exactly 28.349523125 g. (Fluid ounces differ between the US and UK, but those measure volume, not weight.)
Why 14 pounds in a stone? The stone historically varied by town and by what was being weighed; the UK standardized it at 14 lb in the 19th century, and that is the definition still used today.
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