How Many Ounces in a Gallon?
128 fl oz
There are 128 fluid ounces in 1 US gallon (3,785 ml).
UK: 1 imperial gallon (4,546 ml) = 160 imp fl oz
Exact: 1 gal = 128 fl oz
Gallons to Ounces conversion chart
| Gallons | Ounces |
|---|---|
| 0.125 gal | 16 |
| 0.25 gal | 32 |
| 0.5 gal | 64 |
| 0.75 gal | 96 |
| 1 gal | 128 |
| 1.5 gal | 192 |
| 2 gal | 256 |
| 2.5 gal | 320 |
| 3 gal | 384 |
| 4 gal | 512 |
| 5 gal | 640 |
| 6 gal | 768 |
| 7 gal | 896 |
| 8 gal | 1,024 |
| 10 gal | 1,280 |
| 12 gal | 1,536 |
| 15 gal | 1,920 |
| 20 gal | 2,560 |
| 25 gal | 3,200 |
| 50 gal | 6,400 |
| 55 gal | 7,040 |
| 100 gal | 12,800 |
How to convert gallons to ounces
fluid ounces = gallons × 128
Example: 2 gal × 128 = 256 fl oz.
Multiply the gallons by 128 to get US fluid ounces. Without a calculator, halve your way down: half a gallon is 64 fluid ounces, a quarter gallon is 32 fluid ounces, and an eighth of a gallon is 16 fluid ounces.
Larger jugs follow the same rule. 1.5 gallons come to 192 fluid ounces, and a water jug that holds 5 gallons contains 640 fluid ounces.
Keep in mind that these are fluid ounces, a measure of space. Ounces on a kitchen scale are a different unit, as the weight section below shows.
US vs UK gallons and fluid ounces
Two things change in Britain: the gallon is larger and the fluid ounce is smaller. The imperial gallon is split into 160 imperial fluid ounces of 28.41 ml each, while a US fluid ounce is 29.57 ml.
Mixed up, the two systems give awkward numbers. An imperial gallon holds 153.7 US fluid ounces, and a US gallon holds 133.2 imperial ones. Use the imperial figures whenever the recipe or label is British.
| Unit | Size | Used in |
|---|---|---|
| US gallon | 3,785 ml | US |
| imperial gallon | 4,546 ml | UK |
| US fluid ounce | 29.57 ml | US |
| imperial fluid ounce | 28.41 ml | UK |
Does a gallon of water weigh 128 ounces?
No. The ounces in a gallon are fluid ounces, not weight ounces. A US gallon of water weighs about 134 ounces, or 8.35 pounds, because each fluid ounce of water weighs 1.043 ounces on a scale.
The imperial system lines up more closely. An imperial fluid ounce of water weighs 1.002 ounces, and NIST Handbook 44 describes the imperial gallon as the volume of 10 pounds of water under set conditions. For milk and other liquids, use the gallons to pounds converter.
Gallons and ounces: questions
Is 64 oz the same as 1 gallon?
No. 64 fl oz is only half a gallon, so a gallon is twice as big. You would need two containers of 64 fl oz to fill 1 gallon, which also means 64 fl oz is smaller than a gallon, not bigger.
Does 16 oz equal 1 gallon?
Not even close. 16 fl oz is one US pint, and a gallon holds 8 pints. A bottle of 16 fl oz therefore covers 0.125 gallon, so you would pour it 8 times to fill a gallon jug.
Is 32 fl oz 1 gallon?
No, 32 fl oz make one quart, which is 0.25 gallon. A gallon holds 4 quarts, so you would need 4 containers of 32 fl oz to match one gallon jug.
How many 8 oz glasses of water make up a gallon?
A gallon fills 16 glasses of 8 fl oz, or 8 larger glasses of 16 fl oz. That is plain volume math, not a drinking target. For daily needs, the water intake calculator explains the published guidance.
How many fl oz makes 1 gallon?
A US gallon is made of 128 fluid ounces. A British gallon holds 160 imperial fluid ounces instead, each a little smaller than the US ounce, so check which gallon a recipe or label means before you measure.
Related conversions
Sources: Unit definitions: NIST Handbook 44 · Last reviewed · Report an error
https://howmanyounces.com/gallons-to-ounces/