US Gallons to US Fluid Ounces
Convert us gallons to us fluid ounces instantly. 1 gal = 128 fl oz. Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert us gallons to us fluid ounces
To convert us gallons to us fluid ounces, multiply by 128. The relationship is fixed, so the same factor works for any quantity — there is nothing to look up and nothing that changes with temperature, location or context.
fl oz = gal × 128
US Gallons to US Fluid Ounces conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| US Gallons | US Fluid Ounces |
|---|---|
| 1 gal | 128 fl oz |
| 2 gal | 256 fl oz |
| 3 gal | 384 fl oz |
| 5 gal | 640 fl oz |
| 10 gal | 1,280 fl oz |
| 20 gal | 2,560 fl oz |
| 25 gal | 3,200 fl oz |
| 50 gal | 6,400 fl oz |
| 100 gal | 12,800 fl oz |
| 500 gal | 64,000 fl oz |
| 1,000 gal | 128,000 fl oz |
What is a us gallon?
Exactly 231 cubic inches — smaller than the imperial gallon.
What is a us fluid ounce?
A sixteenth of a US pint, about 29.6 mL.
The formula
fl oz = gal × 128
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the US Gallons to US Fluid Ounces
- Type the number of us gallons you want to convert.
- Read the result in us fluid ounces straight away — there is no button to press.
- Check the table below for the values that come up most often, or reverse the conversion with the linked us fluid ounces to us gallons page.
US Gallons to US Fluid Ounces — frequently asked questions
How many us fluid ounces are in a us gallon?
One us gallon equals 128 fl oz. fl oz = gal × 128
What is the formula to convert us gallons to us fluid ounces?
The formula is fl oz = gal × 128. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert us fluid ounces back to us gallons?
Divide instead of multiplying: one us fluid ounce is 0.0078125 gal. The reverse converter is linked in the related tools list.
Is this conversion exact?
Yes. Both units are defined against the same base unit by international agreement, so the factor is exact — any rounding you see is only in the display, which you can widen by entering more decimal places.
Is this us gallons to us fluid ounces free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 15, 2026 · Calculation runs client-side · No data collected · Report an error