Pounds to Ounces Converter

pounds to ounces — quick reference

The formula, worked line by line

The conversion multiplies by sixteen, and the sixteen is a definition. The international avoirdupois pound was fixed at exactly 0.45359237 kilograms in 1959 by agreement between the English-speaking national standards bodies, and the ounce is defined as a sixteenth of it.

Because the relationship is declared rather than measured, the conversion has no error term at all. Any inaccuracy in a weight comes from the scale, its calibration and what is sitting on it, none of which this arithmetic can improve or spoil.

ounces = pounds x 16
1 lb = 0.45359237 kg exactly - 1 oz = 28.349523125 g
1 lb -> 1 x 16 = 16 oz
pounds and ounces: whole part = lb, decimal x 16 = oz
troy: 1 troy oz = 31.1034768 g - 12 troy oz = 1 troy pound

Why sixteen and not ten

Sixteen halves cleanly four times over, which mattered enormously before scales were cheap. A merchant with a balance and a set of weights could measure eighths and sixteenths of a pound by repeated halving, with no arithmetic and no graduated scale, and that is why the number survived into the modern definition.

Ounces of weight, not fluid ounces

A fluid ounce is a volume of about 29.57 millilitres and has nothing to do with the ounce on this page. The two share a name and a rough numerical neighbourhood, which is why a cup of water weighing 8.35 ounces gets mistaken for the eight fluid ounces the cup is defined as.

How to use the pounds to ounces converter

A pound is sixteen ounces, and the sixteen is a definition rather than a measurement. The international avoirdupois pound was fixed at exactly 0.45359237 kilograms in 1959, which makes each of its ounces exactly 28.349523125 grams. Nothing in the conversion is approximate at any number of decimal places.

Sixteen is a convenient number to divide, which is most of why the avoirdupois system survived. Halving a pound four times gives eight, four, two and one ounce, so the common kitchen and shop fractions all land on whole numbers without anyone needing to think about it.

The troy ounce is the exception that catches people out, because it shares the word and not the size. It weighs 31.1034768 grams against the everyday 28.349523125, and only twelve of them make a troy pound. So a troy pound is lighter than an ordinary one while its ounce is heavier.

For everything else the sixteen holds, and the practical use is reading a weight the way the form or the scale wants it. Digital kitchen scales usually offer both a decimal pound and a pounds-and-ounces display, and the second is what a recipe, a shipping label or a birth record expects.

The troy ounce, and why it is heavier

Two ounce systems survived into modern use. The avoirdupois ounce of 28.349523125 grams weighs everything ordinary — food, freight, people, post. The troy ounce of 31.1034768 grams weighs precious metals and gemstones, and it is 9.71 percent heavier than the everyday one.

The pounds go the other way. An avoirdupois pound is sixteen of its ounces, giving 453.59237 grams. A troy pound is only twelve of its ounces, giving 373.2417216. So the troy pound is about 17.71 percent lighter than the ordinary one, even though each troy ounce outweighs an ordinary ounce.

For anyone converting a metal price the practical consequence is direct. A quote of a price per ounce for bullion is per troy ounce, and comparing it against a per-ounce figure for anything else without converting overstates the metal by 9.71 percent.

Reading a weight as pounds and ounces

Most places that use pounds want them written as whole pounds plus a remainder in ounces rather than as a decimal. Birth weights, postal rates, boxing divisions and recipe quantities all take that form, and a scale reading 7.4 pounds has to be translated before it can be written down.

The method is straightforward: the whole number is the pounds, and the decimal part multiplied by sixteen is the ounces. Seven point four pounds is 7 pounds and 0.4 times 16, which is 6.4 ounces, so it is written as 7 pounds 6 ounces once rounded to the nearest ounce.

Shipping is the case where the direction of rounding matters. Carriers generally charge on the next whole unit up, so a parcel at 3 pounds 1 ounce is usually billed as four pounds. Knowing the ounce figure rather than the decimal is what tells you whether removing something from the box saves money.

Every pounds value, worked out

48 common pounds figures each get their own page, with the answer at full precision, the arithmetic, what rounding costs, and the nearest real-world reference point on the scale.

Questions people ask