1/3 Cup Rolled Oats in Grams
1/3 cup of rolled oats weighs about 29.7 g (spooned and levelled, King Arthur Baking). That is 89 g per cup divided by three. That is the number most people come here for. The rest of the page is for the people who want to know why it is approximate, how to measure it properly, and how to use it in a real recipe without a second round of arithmetic.
Rolled Oats is described in the data as follows: Old-fashioned rolled oats, steamed and flattened. It is used for oatmeal, cookies, granola and crumble toppings. Knowing the weight matters because recipes written in cups assume a particular way of filling the cup, and that assumption is invisible until a bake comes out wrong. A cup of a light, airy ingredient can weigh much less than a cup of a dense one, so converting by volume alone tells you nothing about how much of the ingredient is actually in the bowl. Weighing 29.7 g of rolled oats removes that guesswork, and it makes the recipe repeatable: the same weight gives the same result next week, in a different kitchen, with a different set of cups.
The one-third cup is a particularly useful measure because it sits at the centre of the usual scaling steps. Halve two-thirds of a cup and you get one-third. Double one-third and you get two-thirds. Add one-third to two-thirds and you have a full cup. Recipes written for two people, test batches, and scaled-down bakes use it constantly, which is why it deserves its own page rather than a passing mention in a table.
Conversion table for rolled oats
| Amount | Grams (approx.) |
|---|---|
| 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 1/3 cups | 118.7 g |
| 2 cups | 178 g |
Every figure in this table is calculated from the same base value — 89 g per cup, spooned and levelled, from King Arthur Baking — multiplied or divided by the fraction shown. No other source was used, and no figure was guessed. If you need an amount that is not in the table, divide 89 g by the denominator of your fraction, or multiply 29.7 g by the number of third-cups you need: three third-cups make a cup, so three lots of 29.7 g should add up to about 89 g, which is a useful check that your arithmetic and your scale agree.
How to measure one-third of a cup of rolled oats
Cup measures only work when everyone fills the cup the same way. The method in the data file is the reference point, and copying it is what makes the gram figure meaningful. The reference method for rolled oats is spooned and levelled. For a dry ingredient that means spooning it into the measure and levelling the top with the back of a knife, rather than scooping the cup through the bag, which packs it down and adds weight. For a poured ingredient it means pouring to the line and reading the level at eye level. For a scooped ingredient it means pressing it into the measure so there are no air pockets. Copying the method is what makes the 29.7 g figure true; changing the method changes the weight, sometimes by a lot.
A kitchen scale is the simplest way to get this right. Put a bowl on the scale, press tare to zero it, and add rolled oats until the display reads 29.7 g. That is the whole technique, and it takes less time than finding the right measuring cup. If you do not have a scale, use a proper one-third cup measure rather than estimating a third of a larger cup, and level it carefully. Shaking the cup to settle the contents, tapping it on the bench, or heaping it above the rim all change the weight, and with a light ingredient those changes are a large share of the total.
The most common mistake is treating all cups as equal. A US cup is the standard used throughout this page and in the King Arthur Baking data, and it is the cup most English-language recipes mean. If your recipe comes from a country that uses metric cups or imperial measures, check which cup it means before converting, because a different cup size changes every figure on this page. The second most common mistake is measuring a dry ingredient in a liquid jug or a liquid in a dry cup: the two are designed differently, and using the wrong one adds a systematic error to every measurement.
Worked examples
A recipe that needs two-thirds of a cup
Picture a recipe calling for two-thirds of a cup of rolled oats. That is two lots of one-third of a cup, so about 59.3 g. Weighing dry grains in lots is practical because a cup of rolled oats settles differently depending on whether it was poured from a height or scooped from the bag, and a scale removes that variation entirely. Pour the grain into a bowl on the scale until it reads 29.7 g, tare it, and pour again to reach 59.3 g in total. That gives you a repeatable base for a pilaf, a porridge, or a grain bowl, where the liquid ratio depends on the dry weight being right.
Halving a recipe that needs two-thirds of a cup
Halving works cleanly here. A recipe for four that needs two-thirds of a cup of rolled oats becomes one-third of a cup, 29.7 g, for two people. This is the single most useful property of the one-third cup measure: it is exactly half of two-thirds, so halving a recipe that uses two-thirds of a cup lands you on the figure at the top of this page with no awkward fractions left over. Weigh it, cook it, and if the result is right you have a two-person version of the recipe that you can repeat exactly.
Batch cooking with one and one-third cups
If you batch-cook, one and one-third cups of rolled oats is about 118.7 g — four lots of 29.7 g. Weighing in lots lets you check your progress as you go, and it also makes it easy to divide a batch evenly later: if you cooked 118.7 g and want four equal portions, each portion started from 29.7 g of dry rolled oats. Keep the cooked portions in labelled containers, cool them quickly, and reheat them thoroughly. The storage notes below give the keeping time for the dry ingredient; cooked grains keep for a much shorter time, so do not confuse the two.
Method, source, and why the figure is approximate
The base figure for rolled oats is 89 g per cup, measured spooned and levelled and sourced from King Arthur Baking. That pairing of method and source is the whole basis of this page: the weight only means something when you know how the cup was filled and who measured it. A cup of rolled oats that is scooped, packed, sifted, or shaken will weigh something different, and a source that rounds its figures will give a slightly different number from one that does not.
All density-based results on this page are labelled approximate, and they should be treated that way. The honest way to use them is as a starting point for everyday cooking and as a precise-enough guide for most baking, with a kitchen scale as the final check whenever the result matters — a cake for a celebration, a loaf you are selling, a batch you are preserving, or any recipe you plan to repeat. If your own weighing disagrees with the table by a gram or two, trust your scale: it is measuring your ingredient, in your kitchen, today.
It is also worth knowing what this page does not do. It does not claim that every brand of rolled oats weighs exactly 89 g per cup, because brands differ in grind, moisture, and packing. It does not convert other ingredients, and it does not invent a figure for an ingredient that is not in the data. If you need a different ingredient, use its own page, where the same method and the same source discipline apply.
Practical guidance: when this conversion matters most
This conversion matters most when rolled oats is doing structural work in a recipe rather than just adding flavour. In baking, the ratio of dry ingredients to liquid decides whether a cake rises and sets or sinks and stays wet in the middle, and a third of a cup is a large enough amount for a measuring error to change that ratio. In a spice blend or a seasoning mix, the same third of a cup may be the difference between a dish that is balanced and one that is dominated by a single flavour. In batch cooking, small errors multiply: if you are off by a few grams per third-cup and you use four third-cups, the error is four times as large.
When you do not have a scale, the best fallback is to measure carefully with cups and to keep the rest of the recipe consistent: if you measured rolled oats by volume, measure the other dry ingredients by volume too, rather than mixing weighed and cup-measured ingredients in the same bowl. Mixing methods mixes two different kinds of error, and the result is harder to diagnose when something goes wrong. If a bake fails and you measured by volume, the first thing to check is whether the cup was filled the way the recipe assumed — spooned and levelled, packed, or poured — because that is the most common cause of a dry or wet crumb.
A practical habit that costs nothing is to write the gram weight on the recipe the first time you weigh an ingredient. Next time you will not need this page at all for that recipe, and you will have a record of what actually worked in your kitchen. Over time those notes become a personal conversion table that is more accurate for your brands and your equipment than any published table, because it was measured where you cook.
Storage and uses
Airtight container, cool and dry, up to 6 months. Rolled Oats is used for oatmeal, cookies, granola and crumble toppings. Storage matters for conversion accuracy as well as for freshness: an ingredient that has absorbed moisture from the air weighs more per cup than a dry one, and one that has dried out weighs less. Keeping rolled oats in the conditions described in the storage notes — an airtight container, in the right place, for no longer than the keeping time — keeps its weight per cup close to the published figure, which keeps this page accurate for you. If a packet has been open for months in a humid kitchen, weigh it rather than trusting the cup, and replace it if it smells stale, has clumped hard, or shows any sign of spoilage.
Frequently asked questions
How many grams is 1/3 cup of rolled oats?
About 29.7 g, spooned and levelled, according to King Arthur Baking. That comes from 89 g per cup divided by three. The figure is approximate — rolled oats varies a little by brand, grind, and moisture — so verify with a kitchen scale when the amount matters, for example in baking or when you are scaling a recipe.
Is 29.7 g exact?
No. It is an approximate conversion. A cup measures volume and a gram measures weight, so the true weight of one-third of a cup of rolled oats depends on how it was measured, how settled it is, and its moisture content. The 89 g per cup figure from King Arthur Baking is the best available reference, and 29.7 g is that figure divided by three. For everyday cooking the approximation is fine; for precise baking, weigh the ingredient and trust the scale.
How do I measure 1/3 cup of rolled oats without a scale?
Use a one-third cup measure if you have one, and fill it the way the data specifies: spooned and levelled. If you only have a one-cup measure, fill it to the one-third mark, or fill a half-cup measure two-thirds full — though that is harder to judge by eye. Level the top with a straight edge for dry ingredients, and read liquids at eye level. A scale is more accurate, and a basic kitchen scale costs less than a set of measuring cups.
How many grams is 2/3 cup of rolled oats?
About 59.3 g — double the one-third cup figure of 29.7 g. Two-thirds of a cup is the amount that appears most often alongside one-third of a cup in recipes, because halving two-thirds gives one-third and doubling one-third gives two-thirds. Weigh it as two lots of 29.7 g if you want to check your work as you go.
Can I use this conversion for a different brand of rolled oats?
Yes, as a starting point, but expect small differences. Different brands grind, dry, and pack rolled oats slightly differently, and those differences change how much fits in a cup. The King Arthur Baking figure of 89 g per cup is a representative value, not a guarantee for every packet. If a recipe is sensitive — a cake, a loaf, or a preserved batch — weigh your own brand once and note the result for next time.