Ounces to Cups Converter

US fluid ounces to US cups — quick reference

The formula, worked line by line

The arithmetic is a division by eight, and the eight is a definition rather than a rounding. The US liquid gallon is exactly 231 cubic inches, which makes it exactly 3.785411784 litres once the inch is fixed at 2.54 centimetres. Divide by 128 for the fluid ounce and multiply by 8 for the cup.

Because every step in that chain is exact, the conversion introduces no error at all. Any inaccuracy in the final quantity comes from the jug, the pour or the ingredient settling, which is worth remembering before quoting a converted figure to more decimal places than a kitchen can measure out.

cups = US fl oz / 8
1 US cup = 8 US fl oz = 236.5882365 mL
8 fl oz -> 8 / 8 = 1 cup
12 fl oz -> 12 / 8 = 1.5 cups
US ladder: cup = 8 fl oz, pint = 16, quart = 32, gallon = 128

Why a cup of water weighs 8.35 ounces and not 8

A US cup holds 236.59 millilitres. Water is very close to one gram per millilitre, so a cup of it weighs about 236.59 grams. Divide that by the 28.349523125 gram ounce and you get 8.35 ounces, not eight. The two ounces were never the same unit and the near miss is what makes the confusion so durable.

When the conversion is the wrong operation entirely

If a recipe lists an ingredient in both ounces and grams, those are weight ounces and no volume tool applies. The same is true when the instruction is to weigh something. Converting weight ounces to cups requires the density of that specific ingredient, and any tool offering a single factor for it is guessing on your behalf.

How to use the ounces to cups converter

This page answers the volume half of the question. Eight fluid ounces make one US cup, so the conversion is a division by eight and every answer lands on a clean fraction: four ounces is half a cup, two is a quarter, twelve is a cup and a half. Nothing here is approximate, because the cup is defined as eight fluid ounces rather than measured.

The reason the question gets asked at all is that American recipes use the word ounce for two unrelated things. A fluid ounce is a volume, roughly 29.57 millilitres. An ounce is a weight, exactly 28.349523125 grams. The numbers sit close enough together to look like the same unit, and the word fluid is the only signal, which recipes drop.

That gap is the whole problem. A cup of water weighs 8.35 ounces, which is close enough to eight that the coincidence holds and nobody notices. A cup of all-purpose flour weighs about 4.23 ounces. Anyone who assumes a cup is eight ounces of anything will double the flour in a recipe written by weight.

Where the answer is genuinely useful is reading a package. A US soft-drink can is twelve fluid ounces, which is a cup and a half. A pint carton is sixteen, which is two cups. A quart of stock is thirty-two, which is four. Once the fluid ounce is converted, the rest of the US ladder needs no further arithmetic.

Which cup does the recipe mean?

There is more than one cup in circulation, and they disagree by enough to matter. The US customary cup is 236.59 millilitres. The metric cup used in Australia and New Zealand is a round 250, which is 5.67 percent larger. The cup printed on American nutrition labels is 240, a rounding of the US cup that runs 1.44 percent high.

None of those differences will ruin a soup. All of them will show up in a cake, because baking depends on ratios between ingredients rather than absolute quantities, and a 5.67 percent error applied to the liquid but not to the flour changes the hydration of the dough. The safe rule is to use one cup definition for the whole recipe.

That last row is the useful shortcut. British and Irish recipes historically measure by weight rather than by cup, so a recipe written in cups is very likely American and the US cup is the right reading. When a British recipe does use a cup, it usually means the 250 millilitre metric one borrowed from Australian cookbooks.

The pint that changes size at the border

A US pint is sixteen fluid ounces, which is two cups. An imperial pint is twenty imperial fluid ounces, which comes to 568.26 millilitres against the US pint of 473.18. The imperial pint is 20.09 percent larger, so a recipe calling for a pint of stock means noticeably different amounts on the two sides of the Atlantic.

The fluid ounces themselves differ too, in the opposite direction. An imperial fluid ounce is 28.41 millilitres against the US 29.57, making it 3.92 percent smaller. The imperial pint is bigger despite its ounce being smaller, because it contains twenty of them rather than sixteen. That is the detail most conversion tables skip.

Bottle sizes carry the same fingerprint. A 500 millilitre bottle is 2.113 US cups, which is why it never quite matches a recipe written in round cups. American water bottles labelled 16.9 fluid ounces are 500 millilitre bottles converted and rounded, rather than a size anyone chose in ounces.

Every US fluid ounces value, worked out

42 common US fluid ounces figures each get their own page, with the answer at full precision, the arithmetic, what rounding costs, and the nearest real-world reference point on the scale.

Questions people ask