Convert US gallons to US fluid ounces
Enter a value in US gallons to convert it to US fluid ounces.
US gallons to US fluid ounces reference
| US gallons | US fluid ounces |
|---|---|
| 1 gal | 128.0001 fl oz |
| 2 gal | 256.0001 fl oz |
| 5 gal | 640.0003 fl oz |
| 10 gal | 1280.0007 fl oz |
| 25 gal | 3200.0017 fl oz |
| 50 gal | 6400.0034 fl oz |
| 100 gal | 12800.0068 fl oz |
The conversion factor
One US gallon is 128.00006763 US fluid ounces. So to convert, multiply your figure in US gallons by 128.00006763. To go the other way, multiply US fluid ounces by 0.0078125.
Doing it in your head
For a quick estimate, round the factor: roughly "times 128". Use the exact converter above when the number matters.
Where this conversion comes up
Cooking and baking (especially US vs metric recipes), fuel, and container sizes.
See the common unit conversions cheat sheet for the factors worth memorising.
Related tools
Frequently asked questions
How many US fluid ounces are in a US gallon?
1 US gallon = 128.000068 US fluid ounces.
What is the formula to convert US gallons to US fluid ounces?
Multiply the number of US gallons by 128.00006763. To go back the other way, multiply US fluid ounces by 0.0078125.
What is 10 US gallons in US fluid ounces?
10 US gallons = 1280.0007 US fluid ounces. The reference table below lists more common values.
Is this converter accurate?
It uses the internationally defined conversion factors and computes at full floating-point precision, then rounds only the displayed result. For everyday purposes it is exact; for legal, engineering or scientific work, confirm the required number of significant figures.
Does it work offline?
Yes. The conversion runs in your browser with no server call, so it keeps working with no connection, and nothing you enter is uploaded.
Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.