Oats are surprisingly light — one cup of rolled oats weighs only 90 grams, making it one of the lightest dry ingredients by volume. Quick (instant) oats are even lighter at 80 grams per cup because they're cut smaller and have more air between the flakes.
This matters a lot for baking. If a recipe calls for "2 cups of oats" and you're trying to convert to grams, using a generic "1 cup = 240g" converter will give you nearly triple the correct amount. This converter uses accurate, oat-specific weights for reliable results every time.
Whether you're making overnight oats, baking oatmeal cookies, mixing granola, or following a recipe from a different measurement system — pick your oat type, enter the cups, and get exact grams.
How to Use
1. Rolled oats are pre-selected — switch to quick oats if needed
2. Enter cups or use the fraction buttons for common amounts
3. Read the gram weight instantly
4. Switch to "Grams → Cups" for reverse conversion
5. Check the reference table for common oat amounts
Formula
Grams of oats = Cups × Grams per cup
Oat weights per cup:
Rolled oats (old-fashioned): 90 g/cup
Quick oats (instant): 80 g/cup
Typical recipe amounts:
1 serving oatmeal: ½ cup (45g rolled oats)
Overnight oats: ½ cup (45g rolled oats)
Oatmeal cookies (batch): 3 cups (270g rolled oats)
Frequently Asked Questions
How many grams in a cup of oats?
One cup of rolled (old-fashioned) oats weighs 90 grams (3.2 oz). Quick oats weigh about 80 grams per cup because the smaller flakes pack slightly differently. Steel-cut oats are much denser at about 160 grams per cup, but they're usually measured differently in recipes.
What's the difference between rolled oats and quick oats for measuring?
Rolled oats are whole oat groats that have been steamed and flattened into large flakes. Quick oats are the same thing but cut into smaller pieces and rolled thinner. Quick oats weigh less per cup (80g vs 90g) because the smaller pieces create different air gaps. In most baking recipes, you can substitute one for the other — but the texture will change slightly.
How many cups is 100g of oats?
100 grams of rolled oats is about 1.1 cups. For quick oats, 100 grams is about 1.25 cups. This is important for European or Australian recipes that specify oats in grams.
How much oats for one serving of oatmeal?
A standard single serving of oatmeal uses ½ cup (45 grams) of rolled oats with 1 cup of water or milk. This yields about 1 cup of cooked oatmeal. For a heartier serving, use ¾ cup (68 grams) of oats.
How much oats for overnight oats?
The standard overnight oats ratio is ½ cup (45g) rolled oats to ½ cup (120ml) liquid (milk, yogurt, or a mix). This yields one perfect single serving. For two servings, use 1 cup (90g) oats. Quick oats work but get softer overnight — rolled oats hold their texture better.
Can I substitute oat flour in a cups-to-grams conversion?
Oat flour (blended rolled oats) weighs about 92-100 grams per cup — slightly more than whole rolled oats because the ground particles pack together. If you're making your own oat flour by blending rolled oats, start with about 1¼ cups (113g) of whole oats to get 1 cup of oat flour.