How Many Ounces in a Gallon?
There are 128 US fluid ounces in a US gallon. A UK gallon holds 160 imperial fl oz, which is about 153.7 US fl oz.
Gallons to fluid ounces
| Gallons | US fl oz |
|---|---|
| ¼ | 32 |
| ½ | 64 |
| ¾ | 96 |
| 1 | 128 |
| 1 ½ | 192 |
| 2 | 256 |
| 5 | 640 |
US vs UK gallon in ounces
A UK gallon is bigger (4.546 L against 3.785 L), but its fluid ounce is smaller (28.41 ml against 29.57 ml), so it holds 160 imperial fl oz. Counted in US fluid ounces, a UK gallon is about 153.7; a US gallon is about 133.2 imperial fl oz.
Worked example: water bottles in a gallon
A standard water bottle holds 16.9 fl oz (500 ml). 128 ÷ 16.9 = 7.57, so about 7½ bottles make a US gallon.
Fluid ounces vs weight ounces
Fluid ounces measure volume. By weight, a gallon of water ≈ 8.35 lb (3.785 kg) at 4 °C, or about 8.33 lb at room temperature. The 8.35 lb is about 133.5 ounces by weight. Other liquids weigh more or less: a gallon of milk is a little heavier, a gallon of oil lighter.
For smaller amounts, a US quart is 32 fl oz: see how many ounces in a quart.
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Frequently asked questions
How many ounces make one gallon?
128 US fl oz.
Is 128 oz the same as 1 gallon?
Yes, 128 US fluid ounces is exactly 1 US gallon.
How many 32 ounces make a gallon?
4, because 32 fl oz is 1 quart.
How many pounds does a gallon of water weigh?
About 8.35 lb, assuming 1 g per ml. The often-quoted 8.34 lb is that figure rounded down; at room temperature water is about 8.33 lb.