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Volume
Fluid ounces to Gallons
Convert fluid ounces (fl oz) to gallons (gal). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 fl oz = 0.007812 gal
Fluid ounces to Gallons Conversion Table
Common values, ready to copy:
| fluid ounces | gallons |
|---|---|
| 1 fl oz | 0.007812 gal |
| 2 fl oz | 0.015625 gal |
| 5 fl oz | 0.039062 gal |
| 10 fl oz | 0.078125 gal |
| 25 fl oz | 0.195312 gal |
| 50 fl oz | 0.390625 gal |
| 100 fl oz | 0.78125 gal |
| 1,000 fl oz | 7.8125 gal |
Formula
gallons = fluid ounces × 7.81249587e-3
Volume conversions use US customary measure (the cup, fluid ounce, and gallon are US definitions, not imperial). 1 US cup = 236.588 mL, 1 US gallon = 3.785411784 L.
About Fluid ounces and Gallons
Fluid ounces (fl oz): 1/128 of a US gallon, or 29.5735 mL; the UK imperial fluid ounce is slightly different at 28.4131 mL, a remnant of pre-metric British measurement. Common uses: US beverage container sizes (a 12-oz soda can), US liquid recipe measurements, and UK pub measures for spirits (where a 'single' is 25 or 35 mL but historically tracked from imperial fl oz).
Gallons (gal): The US gallon (3.785 L) descends from Queen Anne's 1707 wine gallon; the UK switched to a larger imperial gallon (4.546 L) in 1824, but the US kept the original definition. Common uses: US fuel sales, US milk packaging, lawn and garden chemicals, swimming pool volumes, and aquariums.
How the conversion works
Volume conversions use US customary measure (the cup, fluid ounce, and gallon are US definitions, not imperial). 1 US cup = 236.588 mL, 1 US gallon = 3.785411784 L.
The exact relationship is gallons = fluid ounces × 7.81249587e-3, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.
When this conversion matters
Converting between fluid ounces and gallons comes up wherever volume measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.