Fluid ounces to gallons
One fl oz equals 0.0078125 gal. Type any number and the answer appears as you type — the maths happens in your browser.
Result
The same value in every unit
| Unit | Value |
|---|
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Common values
| fluid ounces | gallons |
|---|---|
| 1 fl oz | 0.0078125 gal |
| 2 fl oz | 0.015625 gal |
| 3 fl oz | 0.0234375 gal |
| 5 fl oz | 0.0390625 gal |
| 10 fl oz | 0.078125 gal |
| 15 fl oz | 0.1171875 gal |
| 20 fl oz | 0.15625 gal |
| 25 fl oz | 0.1953125 gal |
| 50 fl oz | 0.390625 gal |
| 100 fl oz | 0.78125 gal |
| 500 fl oz | 3.90625 gal |
| 1000 fl oz | 7.8125 gal |
How to use
- Enter the number of fluid ounces in the field.
- The result in gallons updates on every keystroke.
- Use the table below for the values people look up most often.
Formula and reverse conversion
The formula
To convert by hand: gal = fl oz ÷ 128. Going back the other way, one gal is 128 fl oz.
Where the odd number comes from
The factor is not a round number because the imperial units are defined through the metric ones by international agreement: an inch is exactly 25.4 mm and a pound is exactly 0.45359237 kg. Everything else follows from those definitions.
gal = fl oz ÷ 128
Frequently asked questions
How many gallons are in one fluid ounces?
One fl oz is 0.0078125 gal.
How do I convert fluid ounces to gallons?
Multiply by the factor: gal = fl oz ÷ 128.
Is the result exact?
The factors are the exact legal definitions, and up to ten significant digits are kept in the answer. Rounding happens only in the display.
How do I convert gallons back to fluid ounces?
One gal is 128 fl oz — or open the reverse page linked below.