How many ounces are in 1 lb?

For most things:

16 ounces are in one pound.

 

For precious metals:

12 troy ounces (31.1g) per troy pound (373g)


Note that there is an ounce, which is a unit of weight, as well as a fluid ounce, which is a measure of volume. There is no direct correspondence between the two ounces, except under certain conditions; the conversion depends on the details of the stuff in the volume. (For example, one fluid ounce of molten lead will weigh more than one fluid ounce of water.)