There are 16 ounces in a pound. In the avoirdupois system used in the United States and the United Kingdom, one pound is legally defined as exactly 0.45359237 kilograms, and it is divided into 16 avoirdupois ounces of about 28.35 grams each.
The older troy pound, still referenced for precious metals, has only 12 troy ounces, but everyday cooking and shipping weights use the 16-ounce avoirdupois pound.
Source: Wikipedia, Pound (mass)