Topic
How many ounces are in a pound?
In the U.S. customary avoirdupois system used for ordinary body weight and many goods, one pound equals 16 ounces.
At a glance
- Avoirdupois pound
- 16 ounces
- Do not confuse with
- Fluid ounce, a volume unit
Overview
The familiar 16-ounces-per-pound relationship refers to avoirdupois mass. The word ounce can also appear in other systems, including fluid ounces for volume and troy ounces for precious metals, so the unit context matters. A fluid ounce is not a unit of mass and cannot be converted to pounds without knowing the substance and density.
Use the correct kind of ounce
Package weights and body weights in the United States generally use avoirdupois ounces and pounds. Recipes and beverage labels can use fluid ounces, which measure volume, so writing only oz without context can be ambiguous.
Mass and volume are different quantities
A pound measures mass, while a fluid ounce measures volume. Converting between them requires the density of the material, which is why 16 fluid ounces of one liquid does not universally equal one pound of mass.
Sources and review
MOOR's explanatory text is supported by the following source links.
- SI Units – Mass — NIST
- SI Units – Volume — NIST