You're standing there. Flour on your hands. The recipe calls for a specific amount of water or sugar, but you can’t find the right measuring cup. Maybe you lost the 1-cup scoop in the back of the junk drawer. Now you’re staring at two different plastic handles, wondering if 1/2 cup plus 1/3 cup actually equals what you need. It’s one of those tiny moments of friction that can actually ruin a delicate souffle or a batch of sourdough if you wing it and get the math wrong.
Math in the kitchen feels different than math in a classroom. It’s tactile.
The Quick Answer: What is 1/2 cup plus 1/3 cup?
Let’s just get the number out of the way. 1/2 cup plus 1/3 cup equals 5/6 of a cup.
In decimals, that is roughly 0.833 cups. If you are looking for a percentage, it’s about 83% of a full cup.
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Most people don't have a 5/6 measuring cup. They don't exist. You might have a 1/8 or a 1/4, but 5/6 is a "ghost measurement" in the culinary world. To get this right without a specialized tool, you basically have to look at what you do have. If you have a tablespoon set, you’re in luck.
Why the Fractions Trip Us Up
Cooking is chemistry. When you combine 1/2 cup plus 1/3 cup, you aren't just adding numbers; you are adding volume. The reason we can't just add the denominators (the bottom numbers) and say it's 2/5 of a cup—which is a common mistake kids make, and honestly, adults do too when they’re tired—is because the "size" of the slice is different.
To add them, you need a common denominator. In this case, it’s six.
$1/2 = 3/6$
$1/3 = 2/6$
$3/6 + 2/6 = 5/6$
It’s simple on paper. It’s annoying when you’re trying to get dinner on the table before 7:00 PM.
How to Measure 5/6 Cup Using Tablespoons
If you really need to be precise because you're baking something finicky like a sponge cake, you should switch to tablespoons. In the United States, 1 cup equals 16 tablespoons. This is a "golden rule" of kitchen conversions.
So, how do we find 5/6 of 16?
It’s about 13 tablespoons and 1 teaspoon.
Wait. Let’s break that down so it’s actually usable.
- 1/2 cup is 8 tablespoons.
- 1/3 cup is 5 tablespoons plus 1 teaspoon.
- Total: 13 tablespoons and 1 teaspoon.
If you use that, you’ll be almost exactly at the 5/6 mark. It's much more accurate than trying to "eyeball" a line slightly below the rim of a 1-cup measure. Kitchen experts like Shirley Corriher, author of Bakewise, often emphasize that these small discrepancies in volume—especially with fats like butter or liquids like milk—can change the protein structure of your bake. A little too much liquid and your cookies spread into pancakes. Too little, and they’re crumbly rocks.
The Liquid vs. Dry Measuring Debate
Here is something most people ignore: 1/2 cup plus 1/3 cup of flour is not the same as the same amount of milk. Technically, the volume is the same, but the way you measure it changes everything.
Dry measuring cups are meant to be leveled off with a flat edge. Liquid measuring cups have that little spout and extra headspace so you don't spill. If you try to measure 1/3 cup of milk in a dry nesting cup, you will almost certainly under-measure because surface tension will keep you from filling it to the absolute brim without a mess.
And flour? Don't even get me started. If you scoop flour directly with the cup, you pack it down. You might end up with 30% more flour than the recipe intended. The "spoon and level" method is better, but weighing it is the only way to be a pro.
What if You Only Have a 1/4 Cup?
Sometimes you’re working with a limited kit. Maybe you're in a vacation rental or your kids took the other cups to the sandbox.
If you only have a 1/4 cup measure, getting to 1/2 cup plus 1/3 cup is a bit of a headache.
1/2 cup is obviously two of those 1/4 cups.
But 1/3 cup? That’s 1.33 of a 1/4 cup.
Basically, you’d need three full 1/4 cups plus about one and a half teaspoons to get close to the total. Honestly, at that point, just go find a tablespoon. It’s easier.
Is 5/6 Cup Close to 3/4 Cup?
A lot of people ask if they can just use 3/4 cup and "add a splash" to make up for the 1/2 plus 1/3 combo.
3/4 is 0.75.
5/6 is 0.83.
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The difference is about 0.08 of a cup, which is roughly 1.3 tablespoons. In a big pot of chili? Doesn't matter at all. In a loaf of bread? That's enough to make the dough too sticky to handle. Don't "splash" it if you're baking.
Real-World Examples of This Measurement
Think about making a standard batch of pancakes. Many recipes call for 1 and 1/3 cups of milk. If you only have a 1/2 cup measure, you’re doing the math in reverse. You’d do two 1/2 cups (to get 1 cup) and then you still need that 1/3.
It's also common in "scaled" recipes. If you find a great recipe that serves 6 people, but you only want to serve 5, you end up with these weird fractional remainders.
The Metric Alternative (The Sanity Saver)
This is why professional chefs like J. Kenji López-Alt or Stella Parks almost exclusively use grams. The imperial system is a mess for scaling.
If you were using a scale:
- 1/2 cup of water is about 118 grams.
- 1/3 cup of water is about 79 grams.
- Total: 197 grams.
See how much cleaner that is? No fractions. No common denominators. Just a number on a screen. If you find yourself frequently struggling with things like 1/2 cup plus 1/3 cup, do yourself a favor and buy a $15 digital kitchen scale. It’ll change your life. Or at least your baking.
Surprising Facts About Cup Sizes
Did you know a "cup" isn't the same everywhere?
In the US, a legal cup for nutrition labeling is 240ml.
In the UK, Australia, and Canada, a "metric cup" is 250ml.
Old British "Imperial" cups were even different than that.
If you’re using a vintage cookbook from the UK and you add 1/2 cup plus 1/3 cup using American tools, you might be off by nearly 10-15ml. It’s usually not a dealbreaker, but it explains why your grandma’s "famous" scones might taste different when you make them at home.
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Actionable Steps for Your Kitchen
Next time you're stuck without the right tools, follow these steps to get your 1/2 cup plus 1/3 cup measurement perfect:
- Use the 13+1 Rule: Measure 13 level tablespoons and 1 teaspoon to get the exact 5/6 cup volume.
- Mark Your Liquid Measuring Cup: If you have a large 2-cup or 4-cup Pyrex, look for the 200ml line. 5/6 of a cup is roughly 197-200ml. It’s a very easy visual shortcut.
- The "Two-Thirds plus a Bit" Hack: If precision isn't vital, two 1/3 cups plus 2 tablespoons will also get you very close.
- Buy a scale: Seriously. Stop fighting with fractions. Weighing your ingredients is faster, more accurate, and results in fewer dishes to wash.
Cooking should be fun, not a math exam. By knowing that 1/2 plus 1/3 lands you at that 5/6 mark, you can stop second-guessing yourself and get back to the actual food.
Check your drawer for that 1/3 cup scoop—it’s probably inside the flour bag. If not, now you know exactly how to work around it.