Ounces to Pounds Converter

The 16-ounce pound is the avoirdupois system, formalized in England in the late 13th century for general trade and inherited by the US. The name comes from the Old French phrase 'avoir de pois' (literally 'goods of weight'), which is how merchants referred to bulk commodities sold by mass. The 16 oz value was fixed for international consistency by the 1959 yard and pound agreement, which defined the international pound as exactly 0.45359237 kg. So 1 lb = 16 oz, 1 oz = 28.3495 g, and these constants are exact, not approximations. This is the pound on every US bathroom scale, kitchen scale, and food label.

It is short for the Latin word 'libra', which meant 'scales' or 'balance' and was also the name of the Roman unit of weight (libra pondo, the 'pound weight'). English inherited the unit and kept the Latin abbreviation, which is why 'lb' looks nothing like the English word 'pound'. The same root gives us the British currency symbol (the pound sterling, originally one pound weight of silver), the astrological sign Libra (the scales), and the Italian word for pound (libbra). The plural 'lbs' is a modern English construction; the strictly correct Latin plural would still be 'lb', but 'lbs' has been the everyday convention for decades.

They are units from different systems. The avoirdupois ounce used for everyday goods is 28.3495 g, and 16 make one avoirdupois pound. The troy ounce used for precious metals is 31.1035 g, and 12 make one troy pound. Gemstones are generally measured in carats, not troy ounces.

Lb + oz notation (e.g. 7 lb 8 oz for a newborn baby) is the standard for everyday US life: birth weight on hospital records, body weight in informal conversation, deli scales, baggage labels, USPS shipping labels, and grocery receipts. Decimal pounds (e.g. 7.5 lb) is what science, engineering, sports performance, and most digital scales report, because it is easier to compute with. The calculator returns both so you can switch contexts: 53 oz becomes both '3 lb 5 oz' (for a USPS shipping label) and '3.3125 lb' (for a spreadsheet or freight quote). One number, two notations, same weight.

Metric prefixes scale units by powers of ten. Grams fit kitchen quantities, kilograms fit body weight and groceries, and metric tons fit freight. The selected unit keeps the number readable without changing the underlying mass.