Gallons to Fluid Ounces Converter
Enter the volume in gallons below to convert it to fluid ounces.
Convert Gallons (US) to Fluid Ounces (US)
Enter a value in gallons (us) (gal (US)) to convert to fluid ounces (us) (fl oz).
Gallon to Fluid Ounce Conversion Table
Table showing various gallon measurements converted to fluid ounces. Click any preset value or arrow to load it into the converter.
| Gallons (US) (gal (US)) | Fluid Ounces (US) (fl oz) |
|---|---|
| 0.5 gal (US) | 64 fl oz |
| 1 gal (US) | 128 fl oz |
| 2 gal (US) | 256 fl oz |
| 5 gal (US) | 640 fl oz |
| 10 gal (US) | 1,280 fl oz |
| 15 gal (US) | 1,920 fl oz |
| 20 gal (US) | 2,560 fl oz |
| 25 gal (US) | 3,200 fl oz |
| 30 gal (US) | 3,840 fl oz |
| 50 gal (US) | 6,400 fl oz |
How to Convert Gallons to Fluid Ounces
To convert gallons to fluid ounces, multiply the volume by the following conversion ratio: 128 fluid ounces/gallon.
Since one gallon is equal to 128 fluid ounces, you can use this simple formula to convert:
The volume in fluid ounces is equal to the volume in gallons multiplied by 128.
For example, here's how to convert 1 gallons to fluid ounces using the formula above.
How Many Fluid Ounces Are in a Gallon?
There are 128 fluid ounces in a gallon, which is why we use this value in the formula above.
Our gallon to fluid ounce calculator automatically converts your volume measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.
Gallons and fluid ounces are both units used to measure volume. Keep reading to learn more about each unit.
What Is a Gallon?
A gallon is a unit of volume equal to 3.7854118 liters (L), the base unit for volume. US liquid gallon defined as exactly 231 cubic inches (3.78541 L). [1]
The gallon is classified as a US customary unit of volume. Gallons can be abbreviated as gal (US); for example, 1 gallon can be written as 1 gal (US).
When working with gallons (gal (US)) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.
In practice, gallons (gal (US)) are widely used across standard volume applications within US customary workflows, engineering documentation, and technical data sheets.
What Is a Fluid Ounce?
A fluid ounce is a unit of volume equal to 0.0295735 liters (L), the base unit for volume. 1/128 of a US gallon (29.5735 mL). [2]
The fluid ounce is classified as a US customary unit of volume. Fluid Ounces can be abbreviated as fl oz; for example, 1 fluid ounce can be written as 1 fl oz.
When working with fluid ounces (fl oz) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.
In practice, fluid ounces (fl oz) are widely used across standard volume applications within US customary workflows, engineering documentation, and technical data sheets.
When converting volume between gallons (gal (US)) and fluid ounces (fl oz), keep full floating-point precision (1 gal (US) = 128 fl oz; 1 fl oz = 0.0078125 gal (US)) during intermediate calculations and round only the final fluid ounce figure to match your instrument tolerance.
More Gallon & Fluid Ounce Conversions
Need to calculate in the opposite direction? Use our fluid ounces (us) to gallons (us) converter (fl oz to gal (US)) to switch your starting unit immediately. You can also explore related tools such as converting milliliters to fluid ounces (us), converting cups (us) to fluid ounces (us), or converting gallons (us) to liters.
Convert from Gallons
Weight and volume require ingredient density (g/mL). Choose a USDA FoodData Central verified ingredient below:
Frequently Asked Questions
References
- [1]NIST OWM StandardNIST OWM (SI Units — Volume)·Volume & Liquid Metrology Standard — Gallons (US) (gal (US)) to Fluid Ounces (US) (fl oz)
- [2]NIST HB 44 SpecificationNIST HB 44 (Liquid & Dry Capacity Tables)·Unit Specifications: Gallon (US Liquid) (gal (US)) & Fluid Ounce (US) (fl oz)
- [3]NIST SP 811 ReferenceNIST SP 811 (NIST SP 811 App. B.9)·Conversion Factors & Mathematical Basis (gal (US) to fl oz)