Pounds to Ounces

The avoirdupois system, from the Anglo-Norman phrase for goods of weight, came into English trade in the late Middle Ages and used a pound of 16 ounces. Sixteen divides cleanly into halves, quarters, eighths and sixteenths, which suited balance scales and market sellers splitting goods by eye. The 1959 international agreement fixed the pound at exactly 0.45359237 kg, which makes the ounce exactly 28.349523125 g.

That halving logic is still visible in American life: a quarter-pound burger patty is 4 oz before cooking, a half-pound of deli turkey is 8 oz, and a stick of butter is 4 oz, one quarter of a one-pound box.

Digital kitchen and postal scales often show decimal pounds, while recipes and newborn records use pounds and ounces. To switch, multiply only the decimal part by 16: 2.5 lb is 2 lb 8 oz, and 3.2 lb is 3 lb 3.2 oz. A baby weighed at 7.5 lb is 7 lb 8 oz, or 3.40 kg.

Reading 2.5 lb as 2 lb 5 oz is the most common error, and it is off by 3 oz. If the scale reads 1.06 lb, that is 1 lb 1 oz, not 1 lb 6 oz.

Gold, silver and platinum are priced in troy ounces of 31.1035 g, about 10% heavier than the ordinary ounce, and a troy pound has only 12 of them. Fluid ounces measure volume, not weight; 16 fl oz of water happens to weigh about 1 lb, but 16 fl oz of honey weighs closer to 1.5 lb.

To come back from ounces, use ounces to pounds. For grams, see pounds to kilograms, or browse every mass unit in the unit converter.