Grams to Cups for Rice, Oats, and Grains

Grains behave differently from flour or sugar in a cup, and the raw-versus-cooked distinction trips people up more than almost any other conversion question.

Reference values for common grains (raw)

Grain	Grams per US cup
White rice (uncooked)	185g
Rolled oats	90g
Quinoa (uncooked)	170g
Cornmeal	155g

Why raw and cooked numbers are completely different

One cup of raw rice absorbs water and roughly triples in volume once cooked, so “1 cup of rice” means something entirely different depending on whether a recipe means it before or after cooking. A recipe that says “2 cups cooked rice” is describing a much smaller amount of raw rice, closer to ⅔ cup, than the wording alone suggests. Always check which state a recipe is referring to before converting.

Oats are lighter than they look

Rolled oats are bulky and full of air, which is why a cup only weighs about 90g, less than half the weight of the same cup filled with rice. This also means oats measured by volume are unusually sensitive to how they’re scooped; a firmly pressed cup of oats can weigh noticeably more than one loosely spooned in. Spoon and Level vs Scoop and Sweep covers that packing gap in more depth for flour, and the same logic applies to any bulky, air-trapping dry ingredient.

Using the calculator for grains

The grams-to-cups converter uses raw-ingredient reference densities, matching how these values are typically listed on packaging and confirmed against USDA FoodData Central. If your recipe specifies a cooked measurement, convert the raw grain amount first, then account separately for the volume change during cooking; the two conversions serve different purposes and shouldn’t be combined into one step.