Quick answer: 1/3 US cup = 2.67 fl oz (2 2/3 fl oz, or about 79 mL).
In US kitchen volume, 1/3 cup equals about 2.67 fluid ounces — the same as 2 2/3 fl oz, or roughly 78.86 mL. Because a US cup is defined as 8 fl oz, the math is simply 8 ÷ 3.
Recipes written in the US sometimes mix volume words (fl oz) and weight words (oz) without flagging the difference. The number 2.67 on this page always refers to fluid ounces. If your recipe weighs ingredients in ounces, jump to the dry-ingredient table below.
Exact conversion formula
fluid ounces = cups × 8
1/3 × 8 = 2.6667 fl oz ≈ 2 2/3 fl oz
1/3 cup to ounces chart
Quick equivalents for 1/3 cup, plus nearby cup fractions you might also see in the same recipe.
| Measure | Equivalent | Notes |
|---|---|---|
| 1/3 cup | 2.67 fl oz | Exact value 2 2/3 fl oz, rounds to 2.67 |
| 1/3 cup | 78.86 mL | Often rounded to 79 mL on metric jugs |
| 1/3 cup | 5 tbsp + 1 tsp | Use when you only have spoon measures |
Common cup fractions to fluid ounces
Reference table for the cup fractions you usually see in US recipes.
| Cups | Fluid ounces | Milliliters |
|---|---|---|
| 1/8 cup | 1 fl oz | 29.57 mL |
| 1/4 cup | 2 fl oz | 59.15 mL |
| 1/3 cup | 2.67 fl oz | 78.86 mL |
| 1/2 cup | 4 fl oz | 118.29 mL |
| 2/3 cup | 5.33 fl oz | 157.73 mL |
| 3/4 cup | 6 fl oz | 177.44 mL |
| 1 cup | 8 fl oz | 236.59 mL |
Fluid ounces vs dry ounces
A fluid ounce is volume; a dry ounce is weight. The 2.67 fl oz answer above only works for liquids — milk, oil, broth, lemon juice, water. Pour 1/3 cup of flour and 1/3 cup of chocolate chips onto a scale and you will get two completely different weights, even though both fill the same measuring cup.
One catch most home cooks miss: a US nutrition label rounds 1 cup to 240 mL, but the legal US customary cup is 236.588 mL. That is why a "1 cup" serving on the back of a carton sometimes lines up with 8 fl oz and sometimes drifts by a milliliter or two. For a single 1/3 cup pour the difference is irrelevant; for a doubled bread recipe it starts to add up.
1/3 cup dry ingredients in ounces (by weight)
Use these as ballpark numbers, not absolutes. Flour weight in particular swings 10–15% depending on whether you scoop, spoon-and-level, or sift, and packed brown sugar can gain a few grams just from how hard you press it down. When a recipe is fussy — bread, macarons, anything with chemical leavening — a kitchen scale is faster and more honest than reading these off a chart.
| Ingredient (1/3 cup) | Approx. weight (oz) | Approx. weight (g) |
|---|---|---|
| All-purpose flour (spooned, leveled) | 1.5 oz | 42 g |
| Granulated white sugar | 2.4 oz | 67 g |
| Brown sugar (packed) | 2.6 oz | 73 g |
| Butter (about 5 1/3 tbsp) | 2.7 oz | 76 g |
| Rolled oats | 1.0 oz | 29 g |
| Chocolate chips | 2.0 oz | 57 g |
If you do not have a 1/3 cup measure
Plenty of measuring sets skip the 1/3 cup, or it is buried in the dishwasher when you need it. Two reliable workarounds:
- 5 tablespoons + 1 teaspoon of liquid. Exactly 1/3 cup, no math needed.
- 2 2/3 fl oz in a glass measuring cup. Aim halfway between the 2 and 3 oz lines, then add a small splash.
For oil and runny liquids the spoon method is more accurate than squinting at a Pyrex cup. For thick things like sour cream or peanut butter, level off a tablespoon at a time so you do not leave half of it stuck inside the spoon.
Related quick kitchen answers
For the metric side, check mL to oz. For the spoon version of the same amount, open how many tablespoons in 1/3 cup.
A note on US vs metric cups
Everything above uses the US customary cup (236.588 mL). Australian recipes use a 250 mL cup, so 1/3 of one is about 83.3 mL — close enough for soup, off by a teaspoon for cake. UK home baking has largely moved to grams; if you are following a Mary Berry or BBC Good Food recipe, weigh the ingredient instead of trying to back-convert.
Need another liquid conversion? Open the Cups to Ounces converter, compare metric values in oz to mL, or browse all kitchen converters.