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Fluid Ounces to Cups Converter

Eight fluid ounces make a US cup exactly — but eight ounces of flour do not.

Conversion table

Fluid ouncesIn cups
0.50.0625 cups
10.125 cups
1.50.1875 cups
20.25 cups
2.50.3125 cups
30.375 cups
40.5 cups
50.625 cups
60.75 cups
70.875 cups
81 cups
91.125 cups
101.25 cups
121.5 cups
151.875 cups

🥤 Cups and ounces

  • 1 US cup8 fl oz = 236.6 mL
  • FDA labelling cup240 mL
  • 1 US fl oz29.57 mL
  • 1 imperial fl oz28.41 mL

Reading ounces correctly

  • If the ingredient is a liquid, an ounce is volume. If it is a solid, it is almost always weight — and the two do not convert without knowing the ingredient.
  • Measure liquids in a spouted jug at eye level; measuring cups for dry goods are made to be filled to the brim and levelled.
  • A US recipe's cup is 236.6 mL, but a nutrition label's cup is a round 240 mL. The 1.4% gap never matters in cooking.
  • British recipes that use fluid ounces mean the imperial ounce, 4% smaller — noticeable only in large quantities.

A relationship with no rounding in it

The US customary cup is defined as exactly eight US fluid ounces, which works out to 236.5882365 millilitres because the fluid ounce is itself defined from the gallon. That is why the conversion needs no memorising: every cup fraction is just a count of ounces, so a half cup is 4 fl oz, a quarter cup is 2 and an eighth is 1. American liquid measuring jugs print both scales on the same wall for this reason, and the marks line up exactly rather than approximately.

The ounce that is not an ounce

The word ounce covers two unrelated units: the fluid ounce, a volume of 29.57 millilitres, and the avoirdupois ounce, a mass of 28.35 grams. They only coincide for water, and only because of an arithmetic accident — a US fluid ounce of water weighs about 1.04 ounces. For everything else the gap is large: a cup of all-purpose flour weighs roughly 4.25 ounces, not 8, so a recipe asking for 8 oz of flour wants two cups, not one. When a recipe gives ounces for a solid ingredient, it means the scale.

Cups around the world

  • US customary cup: 236.6 mL, exactly 8 US fl oz.
  • US legal cup, used on nutrition labels: 240 mL.
  • Metric cup, Australia and New Zealand: 250 mL.
  • Canadian cup, pre-metric: 227 mL, an imperial half-pint.
  • Japanese cup: 200 mL, the standard for rice.
  • The UK abandoned the cup entirely and weighs its ingredients instead.

Cup fractions in ounces

  • 1 cup = 8 fl oz = 236.6 mL.
  • ¾ cup = 6 fl oz = 177 mL.
  • ⅔ cup = 5.33 fl oz = 158 mL.
  • ½ cup = 4 fl oz = 118 mL.
  • ⅓ cup = 2.67 fl oz = 79 mL.
  • ¼ cup = 2 fl oz = 59 mL = 4 tablespoons.

Worked examples

Cans, jugs and recipes

A 12 fl oz can

  1. 12 ÷ 8 = 1.5 cups
  2. 12 × 29.5735 = 355 mL
  3. Which is why cans are labelled 355 mL outside the US

12 fl oz = 1½ cups

A recipe asking for 20 fl oz of stock

  1. 20 ÷ 8 = 2.5 cups
  2. 20 × 29.5735 = 591 mL
  3. Round to 600 mL if using a metric jug

20 fl oz = 2½ cups

Frequently Asked Questions

How many ounces are in a cup?

Eight fluid ounces, exactly, in the US customary system. The definition runs the other way round — the cup is defined as eight fluid ounces — so there is no rounding involved at any point.

Is 8 oz of flour one cup?

No. That reading confuses volume with weight. A cup of all-purpose flour weighs about 4.25 ounces, so 8 ounces of flour is close to two cups. Only for water do the fluid and weight ounce land near the same number.

How many cups is 12 oz?

One and a half cups, which is 355 millilitres — the size of a standard soda can. That is the same volume the rest of the world prints as 355 mL on the same can.

Is a cup always 240 mL?

Only on nutrition labels. The US legal cup used for labelling is a round 240 mL, while the customary cup used in recipes is 236.6 mL. The 1.4% difference is invisible in cooking but explains why the two figures both circulate.

Are UK fluid ounces the same?

No. The imperial fluid ounce is 28.413 mL against the US 29.574 mL, so it is about 4% smaller. In a tablespoon of liquid the difference vanishes; in a pint it is a mouthful.

How many tablespoons in a fluid ounce?

Two, since a tablespoon is half a fluid ounce. That makes a quarter cup four tablespoons and a full cup sixteen, which is the ladder worth memorising.

Sources