US Gallons to Fluid Ounces Converter
gal → fl oz · 🧪 Volume
1 US Gallons = 128.00007 Fluid Ounces
How to convert US Gallons to Fluid Ounces
To convert US Gallons to Fluid Ounces, multiply the value in US Gallons by 128.00007. For example, 5 gal = 640.00034 fl oz.
If you need to convert from US Gallons to Fluid Ounces, the key figure to remember is that one US Gallons equals 128.00007 Fluid Ounces. This page gives you a live calculator, a full reference table, and the underlying formula so you can convert gal to fl oz with complete confidence.
Volume conversions are essential in the kitchen, in science, and in any situation involving liquids or capacity. They're also one of the trickiest areas because US and UK (imperial) measurements share names but differ in size.
Understanding US Gallons and Fluid Ounces
A US gallon (3.785 liters) is noticeably smaller than a UK gallon (4.546 liters) — about 20% less. The same applies to pints, quarts, and fluid ounces. Cups, tablespoons, and teaspoons are the backbone of recipe measurement, while liters and milliliters dominate scientific and most international contexts. This US/UK split is the single biggest source of error in volume conversion.
How accurate is this conversion?
Volume conversions here use the internationally accepted definitions: the US gallon is exactly 3.785411784 liters and the imperial gallon is exactly 4.54609 liters. Always confirm which system a recipe or specification uses before converting.
All conversion factors on ClearUnits are based on internationally recognised standards (the International System of Units, SI, and official definitions). Factors are reviewed for accuracy and the calculator uses full-precision values, rounding only the displayed result.
Quick reference: common US Gallons to Fluid Ounces values
The most frequently searched conversions are 1 US Gallons = 128.00007 Fluid Ounces, 5 US Gallons = 640.00034 Fluid Ounces, 10 US Gallons = 1,280.001 Fluid Ounces, and 100 US Gallons = 12,800.007 Fluid Ounces. The full table further down covers every common value, and the calculator handles any number you need in between.
Pro tip: When following a recipe, check the source country first. A British recipe calling for a pint of liquid means 568 mL, while an American pint is only 473 mL — enough difference to affect the result of baking and sauces.
US Gallons to Fluid Ounces — Conversion Table
| US Gallons (gal) | Fluid Ounces (fl oz) |
|---|---|
| 0.1 gal | 12.800007 fl oz |
| 0.25 gal | 32.000017 fl oz |
| 0.5 gal | 64.000034 fl oz |
| 1 gal | 128.00007 fl oz |
| 2 gal | 256.00014 fl oz |
| 5 gal | 640.00034 fl oz |
| 10 gal | 1,280.001 fl oz |
| 25 gal | 3,200.002 fl oz |
| 50 gal | 6,400.003 fl oz |
| 100 gal | 12,800.007 fl oz |
| 250 gal | 32,000.017 fl oz |
| 500 gal | 64,000.034 fl oz |
| 1000 gal | 128,000.07 fl oz |