Quick answer: 1 Gallon (US) in Fluid Ounce (US)
1 gal equals 128 fl oz. To convert Gallon (US) to Fluid Ounce (US), multiply by 128 using the free calculator above — no signup needed.
Volume & Capacity units
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About Volume & Capacity Converter
The Volume & Capacity Converter converts between 8 different units, including Liter, Milliliter, Cubic Meter, Gallon (US), Quart (US). The base unit is the Liter, and every other unit on this page is defined as an exact multiple of it. Type any value into the calculator above to convert instantly — free, unlimited, no signup and nothing to install.
Common equivalents: 1 Liter = 1000 Milliliter, 0.001 Cubic Meter, 0.264172 Gallon (US).
Scale of this category: the smallest unit is the Milliliter (mL) and the largest is the Cubic Meter (m³).
Last updated: 2026-09-15
Volume & Capacity conversion factors
| Unit | Symbol | Value in Liter |
|---|---|---|
| Liter | L | 1 L = 1 L |
| Milliliter | mL | 1 mL = 0.001 L |
| Cubic Meter | m³ | 1 m³ = 1000 L |
| Gallon (US) | gal | 1 gal = 3.785412 L |
| Quart (US) | qt | 1 qt = 0.946353 L |
| Pint (US) | pt | 1 pt = 0.473176 L |
| Cup (US) | cup | 1 cup = 0.24 L |
| Fluid Ounce (US) | fl oz | 1 fl oz = 0.0295735 L |
Worked Examples
See exactly how the conversion works with real numbers, step by step.
How much is 1 Gallon (US) in Fluid Ounce (US)?
- Multiply 1 by the conversion factor 128
- 1 Gallon (US) = 128 Fluid Ounce (US)
How much is 5 Gallon (US) in Fluid Ounce (US)?
- Multiply 5 by the conversion factor 128
- 5 Gallon (US) = 640 Fluid Ounce (US)
How much is 25 Gallon (US) in Fluid Ounce (US)?
- Multiply 25 by the conversion factor 128
- 25 Gallon (US) = 3200 Fluid Ounce (US)
Quick Conversion Reference Table
| Gallon (US) (gal) | Fluid Ounce (US) (fl oz) |
|---|---|
| 1 gal (Gallon (US)) | 128 fl oz (Fluid Ounce (US)) |
| 2 gal (Gallon (US)) | 256 fl oz (Fluid Ounce (US)) |
| 5 gal (Gallon (US)) | 640 fl oz (Fluid Ounce (US)) |
| 10 gal (Gallon (US)) | 1280 fl oz (Fluid Ounce (US)) |
| 20 gal (Gallon (US)) | 2560 fl oz (Fluid Ounce (US)) |
| 50 gal (Gallon (US)) | 6400 fl oz (Fluid Ounce (US)) |
| 100 gal (Gallon (US)) | 12800 fl oz (Fluid Ounce (US)) |
| 500 gal (Gallon (US)) | 64000 fl oz (Fluid Ounce (US)) |
| 1000 gal (Gallon (US)) | 128000 fl oz (Fluid Ounce (US)) |
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FAQ
How much is 1 Gallon (US) in Fluid Ounce (US)?
1 Gallon (US) = 128 Fluid Ounce (US).
How do I convert Gallon (US) to Fluid Ounce (US)?
Enter your value in Gallon (US) into the converter above and the result in Fluid Ounce (US) appears instantly. 1 gal equals 128 fl oz — just multiply your value by 128.
What is the formula for Gallon (US) to Fluid Ounce (US)?
The formula is: value in Fluid Ounce (US) = value in Gallon (US) × 128. For example, 5 gal × 128 = 640 fl oz.
Is this Gallon (US) to Fluid Ounce (US) converter free and accurate?
Yes. This Gallon (US) to Fluid Ounce (US) converter is 100% free, uses the exact international conversion factor (128), and works on any device with no signup.
How do I convert Fluid Ounce (US) back to Gallon (US)?
To convert back, divide by 128 (or multiply by 0.0078125). You can also use our dedicated How Many Gallon (US) in 1 Fluid Ounce (US)? page for instant results.
Do I need to download an app or sign up?
No. The converter runs entirely in your browser — nothing to install, no account, no fees. It even keeps working offline once the page has loaded.
Which Volume & Capacity units are supported?
This converter supports 8 units: Liter, Milliliter, Cubic Meter, Gallon (US), Quart (US), Pint (US), Cup (US), Fluid Ounce (US).