You're standing in the kitchen, flour up to your elbows, looking at a recipe that demands a measurement your plastic set just doesn't have. It’s a classic culinary roadblock. You've got the 1 cup, the 1/2 cup, and maybe that tiny 1/4 cup rolling around the drawer. But the recipe? It wants two thirds of a cup.
It feels like a math test you didn't study for. Honestly, most standard measuring sets in the U.S. skip the 2/3 and 3/4 increments to save space or production costs. It's annoying. You just want to bake some cookies, not solve for $X$.
But getting this right matters. If you're making soup, "sorta" close is fine. If you're baking a cake? Being off by a few tablespoons is the difference between a moist crumb and a brick. So, let’s break down exactly what two thirds of a cup looks like in the real world, how to hack it with the tools you actually own, and why your liquid and dry measuring cups aren't interchangeable.
The Basic Math of Two Thirds of a Cup
Basically, if you’re looking for the quick answer: two thirds of a cup is roughly 157.7 milliliters. In the United States, we use the customary system. One full cup is 8 fluid ounces. If you do the math—and I’ll save you the headache—two thirds of that is about 5.33 fluid ounces.
It’s a weird number. It doesn't sit cleanly on most lines. If you are using tablespoons, which is usually the easiest way to "build" this measurement, you need 10 tablespoons plus 2 teaspoons. Think about that for a second. It sounds like a lot of scooping. Most people lose count around tablespoon six or seven. If you're like me, you'll start second-guessing yourself halfway through. Wait, was that five or six? Here is how the breakdown looks if you're trying to visualize it:
- In Milliliters: Roughly 158ml (if you want to be precise).
- In Ounces: 5.33 fl oz.
- In Tablespoons: 10 2/3 tablespoons.
- In Teaspoons: 32 teaspoons.
Why You Shouldn't Use a Liquid Cup for Flour
This is where things get messy. There is a massive difference between a liquid measuring cup (the glass one with a spout) and dry measuring cups (the nesting plastic or metal ones).
When you use a liquid cup for dry ingredients like flour or cocoa powder, you can't level it off. You end up shaking the cup to get the top flat, which packs the flour down. Packed flour is heavy flour. You might end up with 20% more than the recipe called for. Your bread will be dry. Your heart will be broken.
On the flip side, trying to measure 2/3 cup of milk in a dry nesting cup is a recipe for a spill. You have to fill it to the absolute brim to get the full measurement. Surface tension only does so much. One slight hand shake and half your milk is on the counter.
How to Measure Two Thirds of a Cup if You Don't Have the Right Scoop
Most of us have a 1/3 cup measure. That’s the easy win. You just use it twice. Simple.
But what if you lost that one? It happens. Those little rings holding sets together are flimsy. If you only have a 1/4 cup and a tablespoon, you’re going to have to do a little "kitchen chemistry."
To get two thirds of a cup using a 1/4 cup measure, you need two of those 1/4 cups, plus 2 tablespoons and 2 teaspoons. It’s a bit of a jigsaw puzzle.
Another way? Use your 1/2 cup measure. Fill it up. Then add 2 tablespoons and 2 teaspoons to it.
If you're working with a scale—which, honestly, is what the pros like King Arthur Baking or J. Kenji López-Alt recommend—you should be measuring by weight. Weight never lies. Volume is a liar. A cup of flour can weigh anywhere from 120 grams to 160 grams depending on how hard you scooped it.
For water or milk, 2/3 cup weighs approximately 157 grams. For all-purpose flour, 2/3 cup weighs approximately 80 to 85 grams.
The Metric Confusion
If you’re following a recipe from the UK or Australia, "two thirds of a cup" might actually mean something slightly different.
The U.S. "legal" cup used for nutrition labeling is 240ml. The U.S. "customary" cup is 236.5ml. In the UK and many Commonwealth countries, they historically used the Imperial cup, which is about 284ml, though many modern recipes there have moved to a metric cup of 250ml.
If you use a 250ml metric cup, two thirds is 166.6ml.
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Is a 9ml difference going to ruin your dinner? Probably not. But if you’re making a delicate French macaron or a complex soufflé, those tiny variances add up. Always check where your author is from. If the recipe uses grams, stop worrying about the "cup" entirely and just use the scale. It's faster and there are fewer dishes to wash.
Common Misconceptions About 2/3 Cup
One of the biggest mistakes people make is assuming that two 1/3 cups is the same as 3/4 cup. It’s not. 2/3 is about 66%, while 3/4 is 75%. That 9% difference is huge in baking.
Another one? Using a coffee mug.
I've seen people do this. They grab a standard mug from the cabinet and fill it "about two thirds of the way."
Mugs are not measuring tools. A standard mug can hold anywhere from 8 to 14 ounces. A "half full" mug could be 4 ounces or 7 ounces. Unless you are making a "dump cake" where precision is a suggestion, put the mug back in the cupboard.
Practical Tips for Precise Measuring
If you have to measure two thirds of a cup of something sticky, like honey or peanut butter, spray your 1/3 cup measure with a little non-stick cooking spray first. The honey will slide right out. If you don't, you'll leave about a tablespoon of it stuck to the plastic, and your "two thirds" will actually be "nine sixteenths" or some other math nightmare.
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When measuring dry ingredients:
- Fluff the ingredient in its container.
- Spoon it into the measuring cup until it overflows.
- Level it off with the back of a butter knife.
- Repeat for the second 1/3 cup.
Never scoop directly with the cup if you can help it. Scooping packs the ingredient.
Real-World Examples of 2/3 Cup in Recipes
You'll see this measurement a lot in "yield-down" recipes. If a recipe for a big family meal is cut in half, you often end up with these weird fractions.
Take a standard pie crust. Often it calls for 1 1/3 cups of flour. If you're making a single crust, you're looking for that 2/3 mark.
Or consider a standard box of Jiffy Corn Muffin Mix. It usually calls for 1/3 cup of milk. If you’re doubling the box because you’re hungry, you need two thirds of a cup.
Conversion Cheat Sheet for Your Kitchen
- 2/3 Cup of Butter: This is 10 tablespoons plus 2 teaspoons. Since a stick of butter is 8 tablespoons, you need one full stick plus 2 tablespoons and 2 teaspoons from a second stick.
- 2/3 Cup of Sugar: About 133 grams. Sugar is denser than flour, so it weighs more.
- 2/3 Cup of Chocolate Chips: Roughly 4 ounces or 113 grams.
Final Steps for Success
To make your life easier going forward, do yourself a favor and buy a high-quality measuring set that actually includes the 2/3 and 3/4 sizes. Brands like Stainless Culinary or Oxo often sell "odd-size" sets. It feels like a luxury until you're in the middle of a recipe and realize you don't have to do any math.
If you're stuck right now with only basic tools:
- Locate your 1/3 cup measure and use it twice.
- If that's missing, use your tablespoon 10 times, then add 2 teaspoons.
- If you have a scale, place a bowl on it, tare it to zero, and pour until you hit 158 grams for liquids or 85 grams for flour.
Precision is the hallmark of a great cook, but adaptability is the hallmark of a smart one. Use the tools you have, keep the ratios consistent, and your dish will turn out just fine.