How Many Grams Are in a Cup of Oats?
One US cup of old-fashioned rolled oats weighs about 89 grams.
Why This One Is Not Exact
Every other conversion on this site is a definition: an inch is exactly 2.54 centimeters, and that never changes. This page is different. A cup measures volume and grams measure weight, and what bridges them is density — which depends on the ingredient and, far more, on how the cup was filled. The figure of 89 grams per cup is the standard reference, not a law of nature.
King Arthur gives the same weight for old-fashioned and quick-cooking oats, since quick oats are rolled from the same groats and simply cut smaller. Steel-cut oats are a different thing entirely and weigh about twice as much per cup.
Where This Comes Up
Oats appear in granola, cookies and porridge, and they are among the lightest things measured by the cup — those flat flakes leave a lot of air between them.
A granola recipe calling for 3 cups of rolled oats wants about 267 grams, usually written as 270 grams.
What People Get Wrong
Steel-cut oats are not interchangeable with rolled oats by volume. They are whole groats chopped rather than flattened, so they are dense grains that weigh roughly twice as much per cup. Quick oats, by contrast, weigh the same as old-fashioned ones.
Rolled Oats Cups to Grams Chart
| Recipe calls for | Grams | Ounces |
|---|---|---|
| 1 tablespoon | 6 | 0.2 |
| 1/8 cup | 11 | 0.39 |
| 1/4 cup | 22 | 0.78 |
| 1/3 cup | 30 | 1.05 |
| 1/2 cup | 45 | 1.57 |
| 2/3 cup | 59 | 2.09 |
| 3/4 cup | 67 | 2.35 |
| 1 cup | 89 | 3.14 |
| 1 1/2 cups | 134 | 4.71 |
| 2 cups | 178 | 6.28 |
| 3 cups | 267 | 9.42 |
| 4 cups | 356 | 12.56 |
Weights follow the King Arthur Baking ingredient weight chart, the reference most American recipes are written against. For the exact, defined conversions used elsewhere on this site, see how we calculate.
Frequently Asked Questions
How many grams is half a cup of oats?
About 45 grams of rolled oats.
Do quick oats weigh the same as rolled oats?
Yes. King Arthur lists old-fashioned and quick-cooking oats at the same 89 grams per cup, because quick oats are rolled from the same groats and only cut smaller.
How much does a serving of oatmeal weigh?
A standard serving is 1/2 cup dry, which is about 45 grams and makes roughly a cup cooked.
What about steel-cut oats?
Steel-cut oats are whole groats chopped rather than rolled, so a cup weighs about 180 grams — twice as much as rolled oats.