There are 28.35 grams in an ounce. The exact figure is 28.349523125 g, but 28.35 is all you'll ever need in a kitchen. That's the weight ounce used for food in the US, and it's a different thing from the fluid ounce on a measuring cup, which we'll get to below.
| Ounces | Grams |
|---|---|
| 1/4 oz | 7.1 g |
| 1/2 oz | 14.2 g |
| 1 oz | 28.35 g |
| 2 oz | 56.7 g |
| 3 oz | 85.0 g |
| 4 oz | 113.4 g |
| 8 oz | 226.8 g |
| 12 oz | 340.2 g |
| 16 oz (1 lb) | 453.6 g |
Where 28.35 grams in an ounce comes from
The ounce in US recipes is the avoirdupois ounce, which is 1/16 of a pound. Since 1959 the pound has been defined in metric terms as exactly 0.45359237 kg, or 453.59237 g. Divide that by 16 and you get 28.349523125 g per ounce. NIST lists 28.35 as the everyday conversion factor.
That definition is why the chart lines up so neatly: 16 oz times 28.349523125 g is exactly one pound.
Going the other way: grams to ounces
To turn grams into ounces, divide by 28.35. A few handy ones:
| Grams | Ounces |
|---|---|
| 10 g | 0.35 oz |
| 100 g | 3.53 oz |
| 250 g | 8.82 oz |
| 500 g | 17.64 oz |
| 1,000 g (1 kg) | 35.27 oz |
For quick mental math, multiplying ounces by 28 gets you close. Rounding up to 30 is fine for a rough idea, but it runs about 6 percent high, which starts to matter in baking.
Ounces vs fluid ounces
This is where a lot of recipes go sideways. An ounce measures weight. A fluid ounce measures volume, about 29.57 ml. They only line up for water and liquids with a similar density, where 1 fluid ounce weighs close to 1 ounce.
For anything else, they drift apart fast. A cup holds 8 fluid ounces, but King Arthur Baking weighs a cup of all purpose flour at 120 g, which is only about 4.2 oz. A cup of honey, on the other hand, weighs far more than 8 oz. So if a recipe says "8 oz flour," it means weight, roughly 227 g, not one cup.
A handy check: King Arthur Baking lists 1/2 cup of butter (one standard stick) at 113 g. That matches 4 oz on the chart, which is the weight printed on most US butter wrappers.
Tips for converting recipes
- Convert once, then write it down. Pencil the grams into the margin so you don't redo the math next time.
- Round sensibly. 113.4 g of butter can be 113 g. Your cookies won't notice.
- Keep small amounts precise. For yeast, salt and spices, a tenth of a gram can matter more than it does for flour.
- Don't mix systems mid recipe. Weigh everything in grams or everything in ounces.
Here's a worked example. Say an older brownie recipe lists 6 oz of chocolate, 4 oz of butter and 12 oz of sugar. Multiply each by 28.35: that's about 170.1 g of chocolate, 113.4 g of butter and 340.2 g of sugar. Round to 170 g, 113 g and 340 g, write them on the card, and you'll never need the calculator for that recipe again.
If you'd rather skip the math entirely, use a scale that switches units. A MeasureMate digital measuring spoon switches between grams, ounces and other units, reads in 0.1 g steps, and weighs up to 500 g, so you can follow a recipe in whichever unit it was written.
Quick questions
Is 1 oz 28 or 30 grams?
It's 28.35 g. Thirty is a rough shortcut that overshoots by about 1.65 g per ounce.
How many grams are in 8 oz?
About 226.8 g. That's 8 times 28.35.
How many ounces are in 100 grams?
About 3.53 oz. Divide the grams by 28.35.
Weights based on NIST conversion factors and King Arthur Baking's ingredient weight chart.