One cup is 8 fluid ounces
A US customary cup holds exactly 8 fluid ounces, so cups and fluid ounces convert with a single number. That covers American recipes, which is where nearly all of this traffic comes from. The one thing to keep straight is that fluid ounces measure volume, not weight.
Quick reference — cups to fluid ounces
| Cups | Fl oz | Cups | Fl oz |
|---|---|---|---|
| ⅛ cup | 1 fl oz | 1 cup | 8 fl oz |
| ¼ cup | 2 fl oz | 1½ cups | 12 fl oz |
| ⅓ cup | 2.67 fl oz | 2 cups | 16 fl oz |
| ½ cup | 4 fl oz | 3 cups | 24 fl oz |
| ⅔ cup | 5.33 fl oz | 4 cups | 32 fl oz |
| ¾ cup | 6 fl oz | 8 cups | 64 fl oz |
A 12 fl oz soda can is 1½ cups; 16 fl oz is 2 cups, or one US pint.
Fluid ounces are not weight ounces
A fluid ounce is a measure of volume; a weight ounce measures mass. They only line up for water. For anything lighter or heavier, the same cup weighs a very different amount.
All three are 8 fluid ounces of volume, yet they weigh from about 4 to 12 weight ounces. Use a scale when a recipe gives dry ingredients in ounces.
Not every cup is 8 ounces
| Standard | Fl oz | Where |
|---|---|---|
| US customary | 8.00 | US recipes |
| US legal | 8.12 | US nutrition labels |
| Metric | 8.45 | Australia, Canada, NZ |
| Imperial | 10.00 | older UK recipes |
An imperial cup is 10 fl oz, so an old British "2 cups" is a fifth more than an American measuring cup. A metric cup is 250 mL against the US cup's 237 mL.
Common questions
How many ounces are in a cup?
One US cup is exactly 8 fluid ounces. Half a cup is 4 fl oz and three-quarters of a cup is 6 fl oz. A metric cup (Australia, New Zealand) is about 8.45 fl oz, and an old imperial cup is 10 fl oz.
Is 8 ounces the same as a cup?
Eight fluid ounces make a cup, yes. But 8 ounces by weight is not a cup unless the ingredient happens to have the density of water. A cup of flour weighs about 4.25 ounces; a cup of honey weighs about 12.
How many ounces are in 1/3 cup?
One-third of a cup is about 2.67 fluid ounces, roughly 2 and two-thirds fl oz, or 5.3 tablespoons.
