89 g of rolled oats is 1 cup. Oats are one of the lightest ingredients per cup because the flakes are flat, irregular and full of air gaps. A cup of oats weighs less than a cup of any flour, which surprises people who assume all dry ingredients are roughly equal, and it is why oatmeal recipes written in grams look so different from the same recipes written in cups.
All figures on this page are approximate, and they come from King Arthur Baking, measured spooned and levelled. When a recipe has to work the first time, verify with a kitchen scale.
Conversion table
| Cups | Grams of rolled oats |
|---|---|
| 1/4 cup | 22.2 g |
| 1/3 cup | 29.7 g |
| 1/2 cup | 44.5 g |
| 2/3 cup | 59.3 g |
| 3/4 cup | 66.8 g |
| 1 cup | 89 g |
| 1 1/2 cups | 133.5 g |
| 2 cups | 178 g |
| 3 cups | 267 g |
| 4 cups | 356 g |
Quick reference: 100 g of rolled oats is about 1.12 cups, and 50 g is about 0.56 cups. All figures are approximate; verify with a kitchen scale when it matters.
How the measurement works
The figure on this page comes from King Arthur Baking, measured spooned and levelled. Old-fashioned rolled oats, steamed and flattened. Oatmeal, cookies, granola and crumble toppings.
All results on this page are approximate. Ingredient weights vary with brand, humidity, temperature and how firmly you pack the cup, so when a recipe has to work the first time, weigh the ingredient on a kitchen scale and use the numbers here as a guide.
Worked examples
Overnight oats for the working week
A batch of overnight oats for five jars uses 445 g of rolled oats, which is 5 cups, one cup per jar. Add a cup of milk and a spoonful of yogurt to each jar and refrigerate overnight. The oats absorb the liquid and soften by morning. Measuring by cups is fine here because the ratio is forgiving and a few grams either way changes nothing.
Oatmeal cookies with a chewy centre
A cookie recipe calls for 178 g of rolled oats, or 2 cups, folded into a butter and sugar dough. The oats give the cookies their chew and their structure. Spoon the oats into the cup and level them without pressing down, because packed oats can add 15 g per cup and make the cookies dry.
A crumble topping for baked apples
A crumble topping needs 89 g of rolled oats, exactly 1 cup, rubbed with butter, flour and sugar. The topping should be loose and pebbly, not a solid sheet. If the oats are short, the topping will be mostly butter and sugar and will melt into a glaze; too many oats and it will be dry and powdery.
Practical guidance
Grains, seeds and similar dry goods should be spooned into the cup and levelled, without shaking or tapping the cup to settle them, which packs them down and inflates the weight. If the recipe calls for rinsed rice or oats, measure before rinsing: the water they absorb changes their weight, and a recipe written for dry weight will not work with wet grain. Store grains in airtight containers in a cool, dry place, and check for a stale or rancid smell before using older stock, because whole grains carry oils that go off faster than refined flour.
Scaling is straightforward once you know the cup weight. Doubling a recipe that calls for 89 g of rolled oats means measuring 178 g, or 2 cups, and tripling it means 267 g, or 3 cups. Halving is just as easy: half a cup is 44.5 g. The key is to scale every ingredient by the same factor, because changing one ingredient without changing the others throws the recipe out of balance. A cake scaled by half still needs half the flour, half the sugar, half the butter and half the rolled oats, not just half of one of them. If you are scaling a recipe by an awkward factor, like two thirds, weigh the rolled oats rather than trying to measure two thirds of a cup in a jug, because the jug markings are not precise enough for fractions of a cup.
When should you weigh rolled oats instead of measuring it? Whenever the recipe has to work the first time, and whenever the amount is large. A kitchen scale costs less than a single failed cake, and it removes the biggest source of variation in home cooking: the way ingredients pack into a cup or a spoon. Put the bowl on the scale, press tare, and add the rolled oats until the display shows the number you need. There is nothing to wash afterwards except the bowl, and the result is the same every time. For small amounts, a level spoon is accurate enough, and for liquids, a jug is fine, but for anything where precision matters, the scale is the tool to reach for.
Storage. Airtight container, cool and dry, up to 6 months.
- Do not tap or shake the cup when measuring oats.
- One cup of oats per jar is the standard overnight oats ratio.
- Store oats airtight and use within six months.
Frequently asked questions
Are rolled oats the same as old-fashioned oats?
Yes. Rolled oats and old-fashioned oats are the same thing: whole oat groats steamed and rolled flat. They weigh 89 g per cup. Instant oats are cut finer and weigh slightly more per cup, and steel-cut oats are much denser at 140 g per cup.
Can I substitute steel-cut oats for rolled oats using this conversion?
No. Steel-cut oats weigh 140 g per cup, and they cook completely differently: they need 30 minutes of simmering, while rolled oats need five. The two are not interchangeable in recipes, even though both are oats.
How do I measure oats accurately?
Spoon them into the cup and level off without tapping or shaking the cup, which settles the flakes and packs them down. For porridge, a scale is actually faster than a cup, because you can pour straight into the pan on the scale.
How many cups of oats do I need for one bowl of porridge?
About half a cup, or 45 g, per person for a standard bowl, with a cup of liquid. Some people prefer a third of a cup for a lighter bowl, and athletes often use a full cup. Start with half a cup and adjust to your appetite.
Do oats go bad?
They can turn rancid because whole oats contain oils. Store them in an airtight container in a cool, dry place and use within six months. If they smell stale or bitter, throw them out.
A note on cup sizes: every figure on this page uses the US cup, which holds 236.6 millilitres. A metric cup, used in Australia and some other countries, holds 250 millilitres, which is about six percent larger, so the same ingredient measured in a metric cup will weigh about six percent more. If your measuring cups are metric, multiply the gram figures here by 1.06, or better still, weigh the ingredient on a scale and skip the cup altogether. The scale does not care which country your cups came from.