The exact factor, and a shortcut you can do in your head
One avoirdupois ounce is exactly 28.349523125 g, because the pound was fixed at 0.45359237 kg in 1959 and there are 16 ounces to the pound. For a fast estimate, divide the grams by 28, or divide by 100 and multiply by 3.5: 200 g → 7 oz, against an exact 7.05.
Common weights in ounces
| Grams | Ounces | What it is |
|---|---|---|
| 10 g | 0.35 oz | two teaspoons of sugar |
| 28.35 g | 1.00 oz | exactly one ounce |
| 100 g | 3.53 oz | a chocolate bar |
| 113 g | 4.00 oz | quarter pound |
| 227 g | 8.00 oz | half pound |
| 250 g | 8.82 oz | quarter kilo |
| 454 g | 16.00 oz | 1 pound |
| 500 g | 17.64 oz | half a kilo |
| 1000 g | 35.27 oz | 1 kilogram |
The whole-number ounces fall on odd gram values: 4 oz is 113.4 g (the "quarter pounder" patty), 8 oz is 226.8 g, and a full pound is 453.6 g.
Two different ounces: food vs precious metals
Everyday weighing uses the avoirdupois ounce (28.35 g). Gold, silver and platinum are priced by the troy ounce (31.10 g), which is about 9.7 percent heavier. If a value looks off for a metal, you are probably mixing the two.
The odd part: the troy ounce is heavier, but a troy pound is only 12 ounces (373 g), so it is lighter than the 16-ounce avoirdupois pound (454 g).
The mistake to avoid
- Ounces measure weight, not volume. An ounce (oz) is 28.35 g of mass; a fluid ounce (fl oz) is 29.57 mL of volume. Similar names, unrelated units.
- Gold "per ounce" means troy. A quoted gold price is always per troy ounce (31.10 g), so an ounce of gold is 9.7 percent more metal than a kitchen ounce.
Common questions
How many ounces is 100 grams?
100 grams is 3.53 ounces (avoirdupois, the everyday ounce). A rough kitchen figure is 100 g is about 3.5 oz.
How do I convert grams to ounces in my head?
Divide the grams by 28, or by 100 and multiply by 3.5. For 200 g: 2 x 3.5 = 7 oz, against an exact 7.05. The error is around 1 percent.
Is a gold ounce the same as a food ounce?
No. Gold is priced in troy ounces of 31.10 g, which are about 9.7 percent heavier than the 28.35 g avoirdupois ounce used for food. Buying an ounce of gold gets you more grams than an ounce of sugar.
