How Many Ounces Are in a Gallon?
There are 128 fluid ounces in 1 US gallon. A half gallon is 64 fl oz, a quart is 32 fl oz, and a pint is 16 fl oz.
Gallons to fluid ounces
| 1/8 gallon (1 pint) | 16 fl oz |
|---|---|
| 1/4 gallon (1 quart) | 32 fl oz |
| 1/2 gallon | 64 fl oz |
| 3/4 gallon | 96 fl oz |
| 1 gallon | 128 fl oz |
| 2 gallons | 256 fl oz |
| 5 gallons | 640 fl oz |
Good to know
These are fluid ounces — a measure of volume, not weight. A gallon of milk weighs about 137 ounces on a scale, but it still contains exactly 128 fluid ounces.
Chasing the "gallon of water a day" habit? That is eight 16-oz bottles, or about six and a half standard 20-oz bottles.
The UK (imperial) gallon is bigger: 160 imperial fluid ounces, about 4.55 liters versus the US 3.79 liters. American recipes and drink math on this page use US measures.
Frequently asked questions
How many ounces are in a half gallon?
There are 64 fluid ounces in half a US gallon.
How many 16.9 oz water bottles make a gallon?
About 7.6 bottles — eight standard 16.9 oz (500 ml) bottles is just over a gallon.
Is 64 oz a gallon?
No — 64 fluid ounces is half a gallon. A full US gallon is 128 fluid ounces.
How many ounces are in a gallon of milk?
A US gallon of milk contains 128 fluid ounces (volume). On a scale it weighs roughly 137 ounces, because milk is denser than water.
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