You're standing in the kitchen, flour on your hands, looking at a recipe that calls for 2/3 cup of water. You reach for the measuring cup. Suddenly, you realize your set only has 1/4, 1/3, 1/2, and 1 cup. Now what? You could guestimate. You could eyeball it. But honestly, if you're baking bread or making a delicate sauce, "close enough" usually leads to a soggy mess or a dry brick.
Knowing exactly how much is a 2 3 cup of water is one of those basic kitchen skills that feels like it should be intuitive, yet it trips up almost everyone at some point. It’s exactly 157.7 milliliters. Or, if you prefer the chaotic energy of Imperial measurements, it's about 5.33 fluid ounces.
Most people just double their 1/3 cup measure. That works. But what if you lost your 1/3 cup under the oven? What if you're trying to weigh your ingredients because you saw a professional chef on YouTube say volume is for amateurs?
The Math Behind the Pour
Let's break the numbers down because precision matters. A standard U.S. "cup" is 8 fluid ounces. If you do the math—and I’ve done it so you don’t have to—two-thirds of eight is $5.333...$. You can’t really measure that third of a decimal with a standard kitchen tool.
In the culinary world, we often simplify this to 5 ounces plus two teaspoons.
If you're using the metric system, which is arguably way more logical, a full cup is generally treated as 240 milliliters in the U.S., though the legal "label" cup is 240ml and the traditional cup is closer to 236ml. To keep your sanity, just aim for 158ml. If you’re in the UK or Australia, their cups are often 250ml, which means their 2/3 cup is roughly 166ml. That 8ml difference might not ruin a soup, but it will definitely change the hydration level of a sourdough starter.
Why You Should Probably Stop Using Dry Measuring Cups for Water
This is the hill I will die on. Stop pouring water into those little nesting metal cups meant for flour.
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Dry measuring cups are designed to be leveled off with a flat edge. You can’t level off water. Surface tension makes the water bulge slightly over the rim—this is called a meniscus—or you spill half of it on the counter while trying to transfer it to the bowl. To get an accurate reading of how much is a 2 3 cup of water, you need a clear liquid measuring cup with a pour spout.
Place that clear cup on a flat surface. Don’t hold it in your hand. If you hold it, your hand tilts. Even a tiny tilt makes the water line hit the 2/3 mark prematurely. Get down on eye level. If the bottom of the curved water line (the meniscus) is touching the 2/3 line, you’re golden.
Converting 2/3 Cup to Spoons and Ounces
Sometimes you're stuck in a rental cabin with a drawer full of mismatched spoons and no measuring cups in sight. It happens.
Here is the breakdown for the desperate:
- Tablespoons: You need 10 tablespoons plus 2 teaspoons. It’s tedious. You’ll probably lose count around tablespoon seven. Use a tally mark on a napkin if you have to.
- Fluid Ounces: 5.3 oz. If you have a baby bottle nearby, those are actually great for measuring small amounts of water in ounces.
- Weight (Grams): This is the gold standard. Water has a density of roughly 1g per 1ml. So, 2/3 cup of water weighs approximately 157 to 158 grams.
I talked to a pastry chef once who refused to use anything but a digital scale. She argued that even the humidity in the room changes how we perceive volume, but weight is constant. She’s right. If you want to know how much is a 2 3 cup of water with 100% certainty, put a bowl on a scale, tare it to zero, and pour until it hits 158g.
The Sneaky Difference Between Liquid and Dry Ounces
This is where people get confused and recipes fail. A "cup" of flour weighs about 120 to 125 grams. A "cup" of water weighs about 236 grams.
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They occupy the same volume, but their mass is totally different. When a recipe asks for 2/3 cup of water, it is asking for volume. However, if the recipe says "5 ounces of water," it’s still usually talking about fluid ounces (volume), not weight. But in professional baking, "ounces" almost always means weight.
Confused yet?
Just remember: Water is heavy. If you’re swapping water for something like milk or heavy cream, the volume (2/3 cup) stays the same, but the weight will shift slightly because of the fats and solids in the dairy. For water, just stick to the 158ml/158g rule and you’ll never have a flat cake again.
Common Mistakes When Measuring 2/3 Cup
I’ve seen people try to use two 1/3 cups of "heaping" water. You can't heap a liquid.
Another big one is using the wrong scale. If you're using a cheap spring scale from the 90s, the needle might be off by half an ounce. Digital is the only way to go. Also, check your altitude. While altitude doesn't change the volume of 2/3 cup of water, it changes the boiling point. If you’re at 5,000 feet, that 2/3 cup of water is going to evaporate much faster in the oven than it would at sea level. You might actually need to add an extra tablespoon to compensate for the dry air and rapid evaporation.
How Much Is a 2 3 Cup of Water in Different Countries?
If you are following a vintage British recipe, be careful. The Imperial cup is larger than the American cup.
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- US Customary Cup: 236.59 ml
- US Legal Cup (on food labels): 240 ml
- Metric Cup (UK, Australia, Canada): 250 ml
So, a 2/3 "metric cup" is actually 166.6ml. If you’re using a British recipe and an American measuring cup, you’ll be short-changing your recipe by about 10ml of water. It doesn't sound like much, but in a bread recipe, that’s the difference between a supple dough and a stiff one.
Practical Hacks for 2/3 Cup Measurements
If you don't have a 1/3 cup measure, use a 1/4 cup and a few tablespoons. It's roughly 1/4 cup plus 6 tablespoons and 2 teaspoons. Okay, that’s actually more complicated.
Honestly? Use a juice glass. Most small juice glasses are about 4 to 6 ounces. A standard 12-ounce soda can is 1.5 cups. If you fill a soda can halfway, you have 3/4 of a cup, which is just a tiny bit more than 2/3. In a survival situation—or just a very poorly equipped Airbnb—filling a soda can slightly less than halfway will get you close enough to 2/3 cup to make a decent pot of rice.
Master the Pour
To truly master how much is a 2 3 cup of water, you have to trust your tools but verify with your eyes.
- Check the markings: Ensure your measuring cup has both milliliters and cups. It makes cross-referencing easier.
- Temperature matters: Hot water expands slightly. If you’re measuring boiling water for a recipe, it might take up a tiny bit more space than ice-cold water, though for 2/3 of a cup, the difference is negligible for home cooking.
- The "Dip and Sweep" is for flour only: Never try to measure water by dipping a cup into a bucket. You’ll get an inaccurate reading every time due to the displacement and the mess on the outside of the cup.
Next time you're in the kitchen, take a second to look at your 2/3 cup of water. It’s more than a splash, less than a full glass. It’s the sweet spot for a single serving of oatmeal or the perfect amount of liquid to deglaze a pan after searing four chicken breasts.
Instead of guessing, go get a digital scale. Set it to grams. Pour until the screen reads 158. Your bread will rise better, your sauces will thicken perfectly, and you’ll finally stop wondering why your "2/3 cup" always looks different every time you cook. Precision isn't just for scientists; it’s for anyone who tired of eating mediocre food.
Stop eyeballing your liquids. Grab a clear glass measuring cup, get down on the floor if you have to so you're at eye level, and watch that meniscus hit the line. It’s a small habit, but it’s the difference between a recipe that works and one that ends up in the trash. Consistent cooking starts with consistent measuring. Now go fix that recipe.