Ounces to Grams Converter

One avoirdupois ounce is exactly 28.349523125 grams, so:

grams = ounces × 28.3495

That long decimal is exact, not rounded — it follows from the pound being defined as 0.45359237 kg and an ounce being one sixteenth of a pound.

Cooking is where this conversion gets used most. 4 oz of butter is 4 × 28.3495 = 113.4 grams, which is why European recipes call for a 113 g or 125 g block where American ones say one stick. 16 oz — a full pound — is 453.59 grams. For postage, a 1 oz letter is 28.35 grams, the threshold that sets the base US first-class rate.

The trap worth flagging:

• Fluid ounces are not ounces. A fluid ounce measures volume, not weight, and only coincides with 28.35 g for water. 8 fl oz of flour weighs about 120 g, not 227 g. If your recipe says "fl oz" or lists a cup measure, this converter is the wrong tool.
• Troy ounces are different again. Precious metals use the troy ounce at 31.103 grams, about 10% heavier. A "1 oz" gold coin is 31.1 g.
• Round to 28.35 for kitchen work. The extra decimals never matter below a kilogram.

To convert grams back to ounces, divide by 28.3495.