A US cup is defined as exactly 8 US fluid ounces, so converting between them is an exact calculation, not an approximation.
How it works
Dividing fluid ounces by 8 gives cups; multiplying cups by 8 gives fluid ounces back. Type into either field and the other updates instantly.
What this does not include
This does not include the UK/imperial cup or fluid ounce, which are defined differently from the US versions used here — a recipe from a UK source using “cups” may not convert with this exact ratio.
How to use this calculator
- Enter a value in either fluid ounces or cups — the other field fills in automatically.
Frequently asked questions
Is a “cup” the same everywhere?
No — the US customary cup (8 fl oz) differs from the UK imperial cup and from a metric cup (250 mL) used in some countries; always check which convention a recipe is using.
Why exactly 8 ounces per cup?
It’s simply how the US customary system defines a cup — a fixed, exact ratio rather than a measured approximation.
Does this work for dry ingredients too?
Only if the recipe is already measuring dry ingredients by fluid volume (common in US recipes) — converting a dry *weight* (like grams of flour) to cups needs the ingredient’s density, not this fluid-to-fluid conversion.
