One-third of a US cup equals 2.67 fluid ounces, or about 80 milliliters.
If you’re asking how much is 1 3 in ounces, the usual kitchen answer is one-third of a cup. In US measures, that comes out to 2.67 fluid ounces. You can also read it as 5 tablespoons plus 1 teaspoon, which is handy when the right cup isn’t on the ring.
The snag is that “ounces” can mean two different things. Fluid ounces measure volume. Plain ounces measure weight. That split is why one-third cup of water and one-third cup of flour do not weigh the same, even though they fill the same space in a measuring cup.
How Much Is 1 3 In Ounces? In A Measuring Cup, It’s 2.67 Fluid Ounces
The math is clean once you know one fact: 1 US cup equals 8 fluid ounces. Divide 8 by 3, and you get 2.666…, which recipes round to 2.67 fluid ounces. Some cooks write that as 2 2/3 fluid ounces.
If you just need the working number and want to get back to the stove, use any of these equal measures:
- 1/3 cup = 2.67 fluid ounces
- 1/3 cup = 5 tablespoons + 1 teaspoon
- 1/3 cup = about 80 milliliters
- 1/3 cup = half of a 2/3 cup measure
Why The Decimal Looks Odd
Thirds almost always turn into repeating decimals. That’s all you’re seeing here. Nothing is off, and your recipe won’t fail because you used 2.67 instead of writing out the long decimal.
In day-to-day cooking, the spoon version is often easier than the decimal version. Five tablespoons plus one teaspoon lands right on one-third cup, so you can skip the calculator and keep moving.
Fluid Ounces And Weight Ounces Are Not Twins
This is where many recipe mix-ups start. A fluid ounce tells you how much space a liquid fills. A weight ounce tells you how heavy something is. When a recipe says “fl oz,” that is volume. When it says “oz” next to meat, cheese, nuts, or chocolate, that is usually weight.
NIST cooking measurement equivalencies list 1/3 cup as about 80 mL, 1 cup as 240 mL, and 1 fluid ounce as 30 mL. The FDA household measure guidance keeps the same split in labeling: cups, fluid ounces, and ounces by weight are separate units, not swap-ins for each other.
That matters most when the ingredient changes shape or density. Water pours flat and steady. Flour can be spooned, scooped, packed, or sifted. Brown sugar can be loose or packed tight. So if you see ounces with a dry ingredient, pause for a second and check whether the recipe writer means weight or volume.
Common Kitchen Conversions Around One-Third Cup
Most cooks don’t need a huge chart. They need the small cluster of numbers that sit close to one-third cup. Once those are in your head, measuring gets quicker and a lot less fussy.
| Measure | Fluid Ounces | Metric Match |
|---|---|---|
| 1 teaspoon | 0.17 fl oz | 5 mL |
| 1 tablespoon | 0.50 fl oz | 15 mL |
| 1/4 cup | 2 fl oz | 60 mL |
| 1/3 cup | 2.67 fl oz | 80 mL |
| 1/2 cup | 4 fl oz | 120 mL |
| 2/3 cup | 5.33 fl oz | 160 mL |
| 3/4 cup | 6 fl oz | 180 mL |
| 1 cup | 8 fl oz | 240 mL |
You don’t need to store every row. The one that pays off most often is 1/3 cup = 5 tablespoons + 1 teaspoon. Right behind it is 1/4 cup = 4 tablespoons, which makes it easy to build one-third cup even when your drawer is missing the piece you want.
Ways To Measure One-Third Cup Without Guessing
Missing the 1/3 cup scoop is no big deal. There are a few clean workarounds, and each one suits a different setup.
Use Spoons For An Exact Fill
What To Count
Measure 5 level tablespoons, then add 1 level teaspoon. That gives you one-third cup on the nose. It works well for oil, milk, melted butter, and other pourable ingredients.
For dry goods, fill each spoon the same way every time. Spoon and level flour if the recipe is touchy. Pack brown sugar only when the recipe says packed. Those little habits do more for texture than a fancy gadget does.
Use A Liquid Cup By The Milliliter Marks
If your liquid cup has metric lines, pour to 80 mL. That is the neatest swap when the ounce marks are busy or hard to read. A lot of measuring cups mark 60 mL, 80 mL, and 120 mL, so one-third cup sits right where you want it.
Use A Scale Only When The Recipe Gives Weight
A scale is great when the recipe lists grams or ounces by weight. It is not the clean answer to every cup question. One-third cup of water is close to 80 mL in volume, yet one-third cup of flour calls for a different weight. If the recipe gives a weight, follow that. If it gives cups, stick with a cup measure unless the writer also gives grams.
Where Cooks Get Tripped Up
Most measuring mistakes around one-third cup come from reading the label too fast. The number looks small, the word “ounces” shows up, and the wrong tool comes out. A few checks can save the batch before it starts.
- Reading “oz” and “fl oz” as if they mean the same thing
- Rounding 2.67 fluid ounces down to 2.5 without meaning to
- Using a dry scoop for sticky liquids and leaving a lot clinging to the cup
- Packing flour hard into the measure when the recipe expects a light fill
- Forgetting that half of a 2/3 cup measure is one-third cup
Recipe wording usually tells you what the writer wants. “1/3 cup milk” is volume. “3 oz cheddar” is weight. “80 mL broth” is volume again. Once you match the unit to the right tool, the rest gets much easier.
Conversions That Save Time Mid-Recipe
These are the swaps that come up when you’re halfway through dinner and do not want to hunt for another measure.
| Tool On Hand | How To Make 1/3 Cup | Result |
|---|---|---|
| Tablespoons + teaspoon | 5 tbsp + 1 tsp | Exact volume |
| 1/4 cup scoop | 1/4 cup + 1 tbsp + 1 tsp | Exact volume |
| 2/3 cup scoop | Fill halfway | Exact volume if leveled |
| Liquid cup with mL marks | Pour to 80 mL | Close kitchen match |
| Recipe written in fluid ounces | Use 2.67 fl oz | Same as 1/3 cup |
If you like printable charts, the NIST Metric Conversion Card is a solid one to bookmark. It keeps fluid ounces, liters, grams, and other kitchen units in one place without turning the page into a wall of numbers.
A Plain Rule To Store
When this question pops up again, go straight to the form of the unit. If the recipe means one-third cup, use 2.67 fluid ounces, 80 mL, or 5 tablespoons plus 1 teaspoon. If the recipe gives ounces by weight, grab a scale and follow the ingredient weight instead of the cup math.
That one split—volume on one side, weight on the other—clears up most kitchen confusion. Once you’ve got that, one-third cup stops feeling awkward and starts feeling easy.
References & Sources
- National Institute of Standards and Technology (NIST).“Metric Kitchen: Cooking Measurement Equivalencies.”Lists household kitchen volume and weight matches, including 1/3 cup, 1 cup, and fluid-ounce conversions.
- U.S. Food and Drug Administration (FDA).“Guidance for Industry: Guidelines for Determining Metric Equivalents of Household Measures.”Gives labeling definitions for cups, fluid ounces, tablespoons, teaspoons, and ounces by weight.
- National Institute of Standards and Technology (NIST).“Approximate Conversions from Metric to U.S. Customary Measures.”Provides a printable conversion reference for volume and weight units used in kitchen math.
