Many times used in some web contents. The most appropriate value would be:
1 Ounce= 28.349523125grams
The avoirdupois ounce is the most commonly used ounce today. It is defined to be one sixteenth of an avoirdupois pound. It is therefore equal to 437.5 grains.
In 1958 the United States and countries of the Commonwealth of Nations agreed to define the international avoirdupois pound to be exactly 0.45359237 kilograms. Consequently, since 1958, the international avoirdupois ounce is exactly 28.349523125 grams by definition.
The ounce is commonly used as a unit of mass in the United States. On January 1, 2000 it ceased to be a legal unit of measure within the United Kingdom for economic, health, safety or administrative purposes but remains a familiar unit, especially amongst older people.