Fluid Ounces to Gallons
Convert fluid ounces to gallons instantly — one fluid ounce is 0.0078125 gallons.
| Fluid Ounces | Gallons |
|---|---|
| 1 fl oz | 0.007812 gal |
| 2 fl oz | 0.015625 gal |
| 3 fl oz | 0.023438 gal |
| 5 fl oz | 0.039062 gal |
| 10 fl oz | 0.078125 gal |
| 25 fl oz | 0.195312 gal |
| 50 fl oz | 0.390625 gal |
| 100 fl oz | 0.78125 gal |
How to use
- Enter a value in the Fluid Ounces field.
- The Gallons figure appears immediately — no button to press.
- Typing in the Gallons field converts back to Fluid Ounces the same way.
- Use the reference table for the values that come up most often.
Fluid Ounces to Gallons formula
To convert fluid ounces to gallons, multiply by 0.0078125.
gal = fl oz × 0.0078125
Put another way, one fluid ounce is exactly 1/128 of a gallon.
Why this factor: the fluid ounce and the gallon are both defined against the liter, so dividing one definition by the other gives 0.0078125 directly. Both definitions are set out in full below.
To go the other way, divide by 0.0078125 — or use the Gallons to Fluid Ounces converter, which is the same calculation reversed.
Worked example
Given 8 fl oz, multiplying by 0.0078125 yields 0.0625 gal.
8 fl oz × 0.0078125 = 0.0625 gal
The converter above does this for any value you type, in either direction.
What is a fluid ounce?
A US fluid ounce is a small liquid volume, one eighth of a cup.
Definition: Exactly one 128th of a US liquid gallon, so exactly 29.5735295625 milliliters.
Where it is used: Beverage cans and bottles, cosmetics, and small liquid quantities in the US.
Worth knowing: Measures volume, not weight — a fluid ounce of water weighs about 1.04 avoirdupois ounces. The imperial fluid ounce is 28.41 mL.
What is a gallon?
A US liquid gallon is the standard large-volume unit in the United States.
Definition: Defined as exactly 231 cubic inches, which works out to exactly 3.785411784 liters.
Where it is used: Fuel sales, milk and beverage containers, and paint in the US.
Worth knowing: The imperial gallon used in the UK and Canada is about 20% larger, at 4.54609 L — so 'miles per gallon' figures are not comparable between the two.
Fluid Ounces vs Gallons
The fluid ounce and the gallon belong to the same family of units, so converting between them is usually a matter of shifting a decimal point or applying a small whole-number factor.
Frequently asked questions
How many gallons are in a fluid ounce?
One fluid ounce equals 0.0078125 gallons.
What is the formula to convert fluid ounces to gallons?
Multiply the number of fluid ounces by 0.0078125. To reverse it, divide by 0.0078125 instead.
How do I convert gallons back to fluid ounces?
Divide by 0.0078125, which is the same as multiplying by 128.
How many gallons are in 10 fluid ounces?
10 fl oz works out to 0.078125 gal.
Is there anything to watch out for with fluid ounces?
Measures volume, not weight — a fluid ounce of water weighs about 1.04 avoirdupois ounces. The imperial fluid ounce is 28.41 mL.
How is the fluid ounce defined?
Exactly one 128th of a US liquid gallon, so exactly 29.5735295625 milliliters.