How this calculator works
The US customary cup is defined as exactly 8 US fluid ounces, so converting cups to fluid ounces is an exact multiplication by 8. These are volume units: a fluid ounce measures space, not the mass an avoirdupois ounce measures on a scale. Imperial fluid ounces differ and are out of scope.
Formula
fluid ounces = cups × 8 (US customary).
Worked example
2.5 US cups to fluid ounces: 2.5 × 8 = 20 fl oz.
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Frequently asked questions
Is a fluid ounce the same as a weight ounce?
No. A fluid ounce is a volume of exactly 29.5735295625 mL, while an avoirdupois ounce is a mass of exactly 28.349523125 g. Water makes them feel similar, but they measure different things.
Does the 8 factor hold for the legal cup too?
No. The 240 mL legal cup on nutrition labels is not defined by fluid ounces; the exact 8-to-1 relationship belongs to the 236.5882365 mL customary cup.
Can I enter part of a cup?
Yes. Decimal cups multiply by 8 the same way, so 0.5 cup gives 4 fl oz.