Ounces to Pounds

About Ounces and Pounds

Ounces (oz): From the Latin uncia meaning one-twelfth (originally 1/12 of a Roman pound, now 1/16 of an avoirdupois pound); the modern avoirdupois ounce is exactly 28.349523125 grams. Common uses: US cooking, postal weight for letters and small parcels, food packaging in the US, and (as a slightly different troy ounce, 31.10 g) the standard unit for precious metals worldwide.

Pounds (lb): From the Roman libra pondo, 'a pound by weight' (the abbreviation lb comes from libra); the avoirdupois pound is exactly 0.45359237 kilograms by 1959 international agreement. Common uses: US body weight, US shipping, US livestock, US agriculture, and athletic equipment in the United States; UK food labeling sometimes still includes pounds alongside the metric kg.

How the conversion works

Mass conversions use the SI definition: 1 pound is exactly 0.45359237 kilograms. The factor above is the exact ratio between ounce and pound.

The exact relationship is pounds = ounces × 6.24999999e-2, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.

When this conversion matters

Converting between ounces and pounds comes up wherever weight & mass measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.