About the fl oz to gal calculation
One fluid ounce is exactly 0.0078125 gallons, so converting between them is a single multiplication. Enter any value above and the result updates as you type. The US fluid ounce. Measures volume, not weight — quite separate from the ounce. The US gallon is 3.785 L. The imperial gallon is 4.546 L — a 20% difference.
Formula
gal = fl oz × 0.0078125
1 fl oz = 0.0078125 gal
1 gal = 128 fl ozWorked example
To convert 8 fl oz, multiply by 0.0078125: 8 × 0.0078125 = 0.0625 gal.
Frequently asked questions
How many gallons are in a fluid ounce?
There are 0.0078125 gallons in one fluid ounce. To convert any amount, multiply the number of fluid ounces by 0.0078125.
How do I convert gallons back to fluid ounces?
Divide instead of multiplying, or equivalently multiply by 128. One gallon is 128 fluid ounces.
Is this conversion exact?
Yes. Since the international agreement of 1959, the relationship between fluid ounces and gallons is defined exactly rather than measured, so the only rounding here is in how many decimal places we show.
Where is each of these units used?
Fluid Ounces: the US fluid ounce. Measures volume, not weight — quite separate from the ounce. Gallons: the US gallon is 3.785 L. The imperial gallon is 4.546 L — a 20% difference.
Sources
- NIST Special Publication 811 — Guide for the Use of the International System of Units