A US gallon is exactly 16 cups
This one is exact, not rounded. A US gallon is defined as 4 quarts, and each quart is 4 cups, so a gallon is 16 cups or 128 fluid ounces. To go back the other way, divide the cups by 16.
The catch: a UK gallon is not the same size
The imperial (UK) gallon is about 20 percent bigger than the US gallon, so it works out to roughly 18.18 US cups instead of 16. Most measuring-cup math online assumes US units, so confirm which gallon you have before scaling a recipe.
Same word, different volume: an imperial gallon is about 2 cups more than a US gallon.
Common US amounts
| US gallons | Cups | Fluid ounces |
|---|---|---|
| ¼ gal | 4 cups | 32 fl oz |
| ½ gal | 8 cups | 64 fl oz |
| 1 gal | 16 cups | 128 fl oz |
| 2 gal | 32 cups | 256 fl oz |
| 3 gal | 48 cups | 384 fl oz |
| 5 gal | 80 cups | 640 fl oz |
Handy for drinks planning: one gallon of punch pours about 16 eight-ounce cups, so a five-gallon jug covers roughly 80 servings.
Two things people get wrong
- US cup vs metric cup. A US cup is 236.6 mL, not the 250 mL used in Australia and much of Europe. For US recipes, treat a cup as about 237 mL.
- Volume, not weight. This converts volume only. It holds for any liquid because 16 cups always fill a gallon, no matter what the liquid weighs.
Common questions
How many cups are in a gallon?
A US gallon holds exactly 16 cups. That is fixed by definition: 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces.
How many cups are in a UK (imperial) gallon?
About 18.18 US cups, because the imperial gallon is roughly 20 percent larger than the US gallon. If a recipe or bottle says "gallon" outside the US, check which one it means.
How many cups in half a gallon?
Eight US cups. Half a gallon is a US half-gallon carton of milk, which is 64 fluid ounces.
