How to convert ounces to grams
To convert ounces to grams, multiply each value by the exact factor in the box: 1 ounce = 28.349523125 grams exactly (1/16 of the international pound). There is no rounding anywhere in the chain — the display trims the final answer to six decimal places, and converting the result back with the inverse page returns your starting number.
The ounce is one sixteenth of the international pound, which fixes it at exactly 28.349523125 grams — a long decimal, but an exact one, inherited from the pound's own definition of 0.45359237 kg divided by 16. It is the unit of American recipes, US postage and a newborn's first weigh-in. The gram it converts into is the unit on nutrition labels, kitchen scales and science worldwide, so the conversion runs constantly in both home and trade.
Recipes are the headline use: 4 oz of cheese is 113.40 g, 8 oz of pasta is 226.80 g, and the 16 oz default on this page — one pound — is 453.59 g, the size of a standard US coffee bag or pasta box meeting a metric scale. Mail is the other: a first-class letter ounce is 28.35 g, so a 55 g European letter needs two ounces of postage. Baby weights quoted as “7 lbs 11 oz” become 3,487 g in a metric health record once the pounds and ounces are each converted and added.
The common mistake is rounding the factor to 28 or 30: at 12 oz, ×28 gives 336 g against the true 340.19 g, enough to throw off bread hydration or a chemical dilution. Watch also for the fluid ounce on packaging — “8 fl oz” of milk is a volume, and its weight in grams depends on the liquid (about 245 g for milk), not on the 226.8 g this page would give for 8 weight ounces. Check whether the ounce is weighed or poured before you convert it.
Worked example
16 ounces is 453.59237 grams: 16 × 28.349523125 = 453.59237 — exactly one pound expressed in grams, which is a useful check that the factor is the real one and not a rounded stand-in.
How to use this converter
- Enter your value in ounces in the box above — the result updates as you type.
- Read the converted value in grams in the headline panel.
- Check the factor, the formula and the inverse result (your answer converted back) in the stats if you need to show your working.
- Use the Ounces to Grams conversion table below for other common values without typing each one.