Gallon (US) to Fluid Ounce (US) Converter
Convert Gallon (US) (gal) to Fluid Ounce (US) (fl oz) instantly. 1 gal = 128 fl oz.
Volume Converter
40 units available
1 gal = 128 fl oz
Formula:
fl oz = gal × 128With your value: 1 gal = 128 fl oz
How big is that?
Everyday references on a logarithmic scale, all expressed in gallon (us) so you can sanity-check the result.
Other Gallon (US) to Fluid Ounce (US) conversions
Gallon (US) to Fluid Ounce (US) Conversion Table
| Gallon (US) (gal) | Fluid Ounce (US) (fl oz) |
|---|---|
| 0.5 | 64 |
| 1 | 128 |
| 2 | 256 |
| 5 | 640 |
| 10 | 1,280 |
| 15 | 1,920 |
| 20 | 2,560 |
| 25 | 3,200 |
| 50 | 6,400 |
| 100 | 12,800 |
| 250 | 32,000 |
| 500 | 64,000 |
| 1000 | 128,000 |
Fluid Ounce (US) to Gallon (US) Conversion Table
| Fluid Ounce (US) (fl oz) | Gallon (US) (gal) |
|---|---|
| 0.5 | 0.003906 |
| 1 | 0.007813 |
| 2 | 0.015625 |
| 5 | 0.039063 |
| 10 | 0.078125 |
| 15 | 0.117188 |
| 20 | 0.15625 |
| 25 | 0.195313 |
| 50 | 0.390625 |
| 100 | 0.78125 |
| 250 | 1.953125 |
| 500 | 3.90625 |
| 1000 | 7.8125 |
Where these values come from
Every factor on this page is traced to the document that defines it. See the full provenance dataset or our methodology.
Gallon (US) (gal)
Volume
The US liquid gallon is exactly 231 cubic inches = 3.785 411 784 L.
National Institute of Standards and Technology (US) · Reviewed 2026-07-01
Fluid Ounce (US) (fl oz)
Volume
Derived from the cubic metre. The litre is exactly 10⁻³ m³; US and imperial capacity units are exact multiples fixed by statute.
Source: NIST Special Publication 811, Guide for the Use of the International System of Units
National Institute of Standards and Technology (US) · Reviewed 2026-07-01
How to Convert Gallon (US) to Fluid Ounce (US)
To convert from Gallon (US) (gal) to Fluid Ounce (US) (fl oz), multiply the value by 128.
Formula: fl oz = gal × 128
Reverse: gal = fl oz × 0.0078125
Step-by-Step Example
- Start with your value in Gallon (US). For example: 5 gal
- Multiply by the conversion factor: 5 x 128
- The result is: 640 fl oz
About Gallon (US)
The US gallon equals approximately 3.785 liters and is the standard unit for fuel and large liquid volumes in the United States.
Fun Fact: The US gallon is about 20% smaller than the imperial (UK) gallon.
Common uses: fuel (US), beverages, swimming pools.
About Fluid Ounce (US)
The US fluid ounce equals approximately 29.57 mL. It is commonly used for beverage and liquid measurements.
Common uses: beverages, cooking, cocktails.
Frequently Asked Questions
How many Fluid Ounce (US) are in 1 Gallon (US)?
There are exactly 128 Fluid Ounce (US) in 1 Gallon (US). This means the conversion factor from Gallon (US) to Fluid Ounce (US) is 128.
What is the formula to convert Gallon (US) to Fluid Ounce (US)?
The formula to convert Gallon (US) to Fluid Ounce (US) is: fl oz = gal × 128. For example, to convert 10 Gallon (US) to Fluid Ounce (US), you would multiply 10 by 128.
What is a Gallon (US)?
The US gallon equals approximately 3.785 liters and is the standard unit for fuel and large liquid volumes in the United States.
What is a Fluid Ounce (US)?
The US fluid ounce equals approximately 29.57 mL. It is commonly used for beverage and liquid measurements.
What are the common uses of Gallon (US)?
The Gallon (US) is commonly used in fuel (US), beverages, swimming pools.
Related Volume Conversions
Cite this page
UnitConvertLab. (2026). Gallon (US) to Fluid Ounce (US) converter. UnitConvertLab. Retrieved from https://unitconvertlab.com/convert/gallon_us-to-fluid_ounce_us