Pounds, ounces and kilograms
Since 1959 the avoirdupois pound has been defined as exactly 0.45359237 kg, so every factor on this page is exact. One pound is 16 ounces, which makes an ounce 28.349523125 g. One kilogram is 2.20462 lb, or 2 lb 3.27 oz. A stone, still used in the UK and Ireland for body weight, is 14 lb = 6.35 kg. A US ton, sometimes called a short ton, is 2,000 lb = 907.18 kg; a metric ton (tonne) is 1,000 kg = 2,204.62 lb; and the British long ton is 2,240 lb = 1,016 kg, which the converter does not list because it is rarely used in the US.
The converter works in grams internally, so tiny and huge numbers are both handled. Enter a value, pick the units, and the table shows the same weight in every unit at once, with a pounds-and-ounces line for anything that a bathroom scale, a baby scale or a shipping label would show that way.
Worked examples
Body weight: 70 kg x 2.20462 = 154.3 lb, or 154 lb 5 oz; 11 stone is 154 lb = 69.85 kg. A newborn weighing 3.4 kg is 7 lb 8 oz (3,400 / 28.3495 = 119.9 oz; 7 x 16 = 112, leaving 7.9 oz). Groceries: a pound of ground beef is 454 g, and a 250 g stick of European butter is 8.8 oz, a little more than two US sticks (4 oz each). Shipping: USPS and UPS charge by the pound and ounce, so a 1.2 kg package is 2 lb 10.3 oz and bills as a 3 lb parcel.
Gym and cargo: a 20 kg barbell plate is 44.1 lb, and a 45 lb plate is 20.4 kg. A pickup with a 1,500 lb payload can carry 680 kg. A 2-ton truck rating means 4,000 lb (1,814 kg), not 2 metric tons.
Ounce confusion and other caveats
Three different ounces exist. The avoirdupois ounce (28.35 g) is the one used for food, mail and body weight, and it is what this converter uses. The troy ounce (31.1035 g) is used for gold, silver and other precious metals, so a one-ounce gold coin actually weighs 31.1 g. The fluid ounce is a volume, not a weight: 8 fl oz of water weighs about 8.3 oz, but 8 fl oz of flour weighs closer to 4.4 oz.
Medication doses are usually in milligrams, and 1 mg = 0.001 g; a 500 mg tablet is half a gram. If a recipe lists ingredients in grams and you only have a cup measure, the conversion depends on the ingredient, not just the unit, so use a kitchen conversion chart rather than a plain weight converter. The results here are shown to eight significant digits; round as needed.