US gallon
1 US liquid gallon = 231 cubic inches = 128 US fl oz. Common for recipes, nutrition labels, and everyday US measurements.
Volume converter
How many oz are in a gallon?
One US liquid gallon equals 128 US fluid ounces. Use this refined tool to switch between ounces and gallons instantly, explore quart/pint/cup equivalents, and compare US versus UK measurements.
128
US fl oz in 1 US gallon
Imperial gallon
1 UK (imperial) gallon = 160 UK fl oz. Use this when referencing UK or Commonwealth fuel economy numbers.
Metric context
1 US gallon = 3.785 liters. 1 liter = 33.814 US fl oz. Toggle between all of them below without leaving the page.
Interactive calculator
Gallons ↔ Ounces
gal
fl oz
Live summary
1.00 gallons = 128.00 ounces
That is also the same as 4 quarts, 8 pints, or 16 cups.
4
Quarts
8
Pints
16
Cups
3.79
Liters
Need imperial? 1.00 UK gallon = 160 UK fl oz.
Reference chart
Common gallon ⇄ ounce conversions
| US gallons | US fl oz | Quarts | Pints | Liters |
|---|---|---|---|---|
| 0.25 | 32 | 1 | 2 | 0.95 |
| 0.5 | 64 | 2 | 4 | 1.89 |
| 1 | 128 | 4 | 8 | 3.79 |
| 1.5 | 192 | 6 | 12 | 5.68 |
| 2 | 256 | 8 | 16 | 7.57 |
| 3 | 384 | 12 | 24 | 11.36 |
| 5 | 640 | 20 | 40 | 18.93 |
| 10 | 1280 | 40 | 80 | 37.85 |
Questions people ask
FAQ: ounces & gallons
Is a gallon always 128 ounces?
128 US fluid ounces applies to the US liquid gallon. The imperial gallon used in the UK and Canada equals 160 UK fluid ounces (which are slightly larger than US ones). The calculator shows both.
How do I convert ounces to gallons quickly?
Divide the number of ounces by 128 to get US gallons. For example, 320 oz ÷ 128 = 2.5 gallons. The input above performs the math automatically and rounds to your preferred precision.
What about cups or liters?
1 gallon = 16 cups and about 3.785 liters. The live summary chips update those equivalents every time you move the slider or type a new value.
Does temperature change the conversion?
Fluid ounces and gallons are volumetric units, so the relationship stays fixed (128:1) for practical kitchen and fuel calculations. Only highly precise laboratory work factors in temperature-driven density changes.