When to use this converter
Use it for body weight in pounds, kilograms or stone, for recipe ingredients in grams or ounces, for shipping weights, and for anything sold by the metric tonne. The result updates as you type, and the swap button converts straight back.
Where the numbers come from
The international avoirdupois pound is defined as exactly 0.45359237 kilograms. The ounce is one-sixteenth of a pound and the stone, still common for body weight in the UK and Ireland, is 14 pounds. The metric tonne is 1,000 kilograms — not to be confused with the US short ton of 2,000 pounds.
Weight or mass?
Strictly, kilograms and pounds measure mass, while weight is a force. In everyday use — on scales, labels and in recipes — the two are treated as the same thing, and so does this converter. Troy ounces used for precious metals are a different unit and are not included. The BMI calculator takes body weight in pounds, and the volume converter handles cups and milliliters.
Worked examples
Body weight: 70 kg × 2.2046226218 ≈ 154.3 lb, and 180 lb × 0.45359237 ≈ 81.6 kg. A UK reading of 11 stone 6 pounds is 160 lb, or about 72.6 kg. The kilograms to pounds and pounds to kilograms pages have ready-made tables.
Baking: a 250 g block of butter is about 8.8 oz, close to two US sticks (8 oz). Weighing flour in grams is more consistent than using cups, because how tightly flour is packed changes how much fits in a cup. See grams to ounces and ounces to grams.
Shipping and luggage: a 23 kg checked-bag limit is about 50.7 lb, and many carriers round it to 50 lb. Postage often steps up by the ounce, so ounces to pounds helps when a scale reads in ounces only.
Precision: kitchen scales usually resolve 1 g or 0.1 oz, and bathroom scales 0.1 kg or 0.2 lb, so reporting a converted body weight to more than one decimal place adds digits the scale never measured. Round the converted figure to match the precision of the original reading.