Direct conversion
Convert gallon (US) [gal US] to fluid ounce (US) [fl oz US] instantly with formula, examples, chart, and FAQs.
1 gallon (US) [gal US] = 128 fluid ounce (US) [fl oz US]
1 gallon (US) [gal US] = 128 fluid ounce (US) [fl oz US]
Example: 1 gallon (US) [gal US] equals 128 fluid ounce (US) [fl oz US].
Volume conversions use cubic metre as the reference unit. US liquid units, metric litres, and cubic units are converted with fixed factors stored in the unit table.
Displayed results are rounded for readability. The calculator keeps enough precision for everyday use and switches to scientific notation for very large or very small values. Last reviewed: 2026-05-21.
The US gallon is a liquid volume unit equal to exactly 3.785411784 liters.
HistoryThe US gallon developed from older English wine-gallon measures and differs from the UK imperial gallon.
Current useUS gallons are common for fuel, water, paint, tanks, pools, and household liquid measurements in the United States.
The US fluid ounce is a liquid volume unit equal to 29.5735295625 milliliters.
HistoryFluid ounces developed from customary liquid measures and differ from imperial fluid ounces.
Current useUS fluid ounces are used for beverages, medicine labels, recipes, cosmetics, and packaged liquids.
| gallon (US) [gal US] | fluid ounce (US) [fl oz US] |
|---|---|
| 1 | 128 |
| 2 | 256 |
| 5 | 640 |
| 10 | 1280 |
| 20 | 2560 |
| 25 | 3200 |
| 50 | 6400.000001 |
| 100 | 12800.000001 |
| 1000 | 128000.000011 |
Use this formula: 1 gallon (US) [gal US] = 128 fluid ounce (US) [fl oz US] Enter your value in the calculator and the result updates instantly.
1 gallon (US) [gal US] equals 128 fluid ounce (US) [fl oz US].
Yes. Use the swap button in the calculator or open the related reverse conversion link when it is listed on this page.