One cup of rolled oats is 3.1746566 ounces, so converting cups of rolled oats to ounces means multiplying by 3.1746566. That factor is specific to this ingredient — it comes from its density, not from any relationship between the two units.
Water is the yardstick: 1 mL of it weighs 1 g. Rolled oats comes in at 0.38041 g per mL, or 38.04% of water, which is why a cup of it is 90 g rather than 236.6 g. Volume and weight only line up for water, and only in metric.
A cup of rolled oats is 90 g when it is measured the standard way, but how it gets into the cup changes the answer: between about 81 g and 108 g covers the range from lightly spooned to firmly packed. That 20% spread is larger than most of the adjustments recipes fuss over, and it disappears entirely the moment the ingredient is weighed instead.
One cup of rolled oats is 3.175 oz. US kitchen scales usually step in eighths of an ounce, which is 3.54 g — around 3.94% of a cup of this ingredient, so the scale is precise enough for a full cup and coarse for a spoonful. That is why recipes mix the two systems: ounces for the bulk, spoons for the small amounts.
How the figure is arrived at: Old-fashioned flakes. Very light for their volume because of the air trapped between them.
The formula
cups- The amount of rolled oats you are converting, in cups
3.17465657546- Ounces per cup for rolled oats, from its density of 0.38041 g/mL
ounces- The equivalent quantity in ounces
How it works, step by step
- Enter the quantity in cups.
- It is multiplied by 3.17465657546, the ounces-per-cup figure for rolled oats.
- The result appears in ounces, with a second reading in g beneath it.
- Use the measure table if you want a standard recipe quantity rather than a number you type in.
Worked examples
1/3 cup of rolled oats in ounces
A recipe calling for 1/3 cup of rolled oats needs 1.05822 ounces on the scale. The arithmetic is 0.333333 × 3.1746566 = 1.0582189, and halving the recipe halves the weight to 0.529109 ounces.
3/4 cup of rolled oats in ounces
A recipe calling for 3/4 cup of rolled oats needs 2.38099 ounces on the scale. The arithmetic is 0.75 × 3.1746566 = 2.3809924, and halving the recipe halves the weight to 1.1905 ounces.
3 cup of rolled oats in ounces
A recipe calling for 3 cup of rolled oats needs 9.52397 ounces on the scale. The arithmetic is 3 × 3.1746566 = 9.5239697, and halving the recipe halves the weight to 4.76198 ounces.
How to read your score
Frequently asked questions
How many ounces are in 1 cup of rolled oats?
One cup of rolled oats is 3.1746566 ounces. Half that quantity is 1.58733 ounces and double it is 6.34931 ounces, so the figure scales straight up and down — there is no offset in this conversion, only the factor.
Why is a cup of rolled oats not 236 g like water?
Because weight per cup depends on what is in the cup. Rolled oats has a density of 0.38041 g per mL where water has 1.00, so a cup of it weighs 90 g rather than 236.6 g. That is a difference of 146.6 g per cup, and it is the reason a single volume-to-weight factor cannot be applied to every ingredient.
Does how I measure it change the weight?
Yes, and by more than most people expect. Handling changes the weight of a cup of rolled oats by roughly 20% — about 9 g either side of 90 g — because old-fashioned flakes. Weighing removes the question entirely.
Is a fluid ounce of rolled oats the same as an ounce?
No. A fluid ounce is a volume — one eighth of a US cup, 29.57 mL — and an ounce is a weight. One fluid ounce of rolled oats weighs 0.3968 oz, so the two readings differ by 60.3%. They coincide only for something with the density of water, and then only roughly.
Is this a US cup or a metric cup?
US customary: 236.59 mL, which is the cup every US recipe means. A metric cup is 250 mL, so the same cup of rolled oats would weigh 95.102 g instead of 90 g — 5.1 g more, or 5.67%. Australian and some European recipes use the metric cup, and the difference is large enough to matter in baking.
Do I need a scale for this, or will measuring cups do?
A scale, if the result matters. Volume measuring carries a spread of about 20% for rolled oats — roughly 18 g on a 90 g cup — while a domestic scale is accurate to a gram or two. For anything where the ratio of ingredients drives the outcome, bread and pastry above all, weigh it.
How many cups of rolled oats is 16 oz?
16 oz of rolled oats is 5.0399 cups — 0.314995 cups to one ounce, so 16 × 0.314995 = 5.0399. Going that way is a division by 3.17466, or a multiplication by 0.314995 if you prefer.
Rolled oats in cups and ounces
| Cups | Ounces | Unrounded |
|---|---|---|
| 1/8 cup | 0.396832 oz | 0.3968320719 |
| 1/4 cup | 0.793664 oz | 0.7936641439 |
| 1/3 cup | 1.05822 oz | 1.058218858 |
| 1/2 cup | 1.58733 oz | 1.587328288 |
| 2/3 cup | 2.11644 oz | 2.116437717 |
| 3/4 cup | 2.38099 oz | 2.380992432 |
| 1 cup | 3.17466 oz | 3.174656575 |
| 1 1/2 cup | 4.76198 oz | 4.761984863 |
| 2 cup | 6.34931 oz | 6.349313151 |
| 3 cup | 9.52397 oz | 9.523969726 |
| 4 cup | 12.6986 oz | 12.6986263 |
Based on 90 g per cup of rolled oats. One cup of rolled oats is 3.1746566 ounces.
| Measure | Grams | Ounces | Millilitres |
|---|---|---|---|
| 1 cup | 90 g | 3.17 oz | 236.6 mL |
| 3/4 cup | 67.5 g | 2.38 oz | 177.4 mL |
| 2/3 cup | 60 g | 2.12 oz | 157.7 mL |
| 1/2 cup | 45 g | 1.59 oz | 118.3 mL |
| 1/3 cup | 30 g | 1.06 oz | 78.86 mL |
| 1/4 cup | 22.5 g | 0.794 oz | 59.15 mL |
| 1 tbsp | 5.625 g | 0.198 oz | 14.79 mL |
| 1 tsp | 1.875 g | 0.0661 oz | 4.929 mL |
US customary measures: 1 cup = 236.59 mL, 1 tbsp = 14.79 mL, 1 tsp = 4.93 mL.
| Ingredient | Grams per cup | Ounces per cup | Density (g/mL) |
|---|---|---|---|
| Panko breadcrumbs | 60 g | 2.116 oz | 0.2536 |
| Cocoa powder | 85 g | 2.998 oz | 0.3593 |
| Rolled oats (this page) | 90 g | 3.175 oz | 0.3804 |
| Oat flour | 92 g | 3.245 oz | 0.3889 |
| Almond flour | 96 g | 3.386 oz | 0.4058 |
| Rye flour | 102 g | 3.598 oz | 0.4311 |
| Dry breadcrumbs | 108 g | 3.81 oz | 0.4565 |
Ordered by weight. The spread across this group is why a single generic cups-to-grams factor cannot work.