---
title: "US gallons to US fluid ounces — gal to fl oz converter"
description: "1 US gallon = 128 US fluid ounces. Convert US gallons to US fluid ounces with a full conversion table, the exact formula, and a calculator for any value."
url: https://atoneplace.net/convert/gallons-to-fl-oz/
site: "At One Place"
---

# US gallons to US fluid ounces

**1 US gallon in US fluid ounces: 1 gal = 128 fl oz**

fl oz = gal × 128

To convert US gallons to US fluid ounces, multiply by 128. The table below gives the values people look up most often, and the converter works for any number.

## US gallons to US fluid ounces table

*Common US gallon values converted to US fluid ounces.*

| US gallons | US fluid ounces |
| --- | --- |
| 1 gal | 128 |
| 2 gal | 256 |
| 3 gal | 384 |
| 4 gal | 512 |
| 5 gal | 640 |
| 10 gal | 1,280 |
| 15 gal | 1,920 |
| 20 gal | 2,560 |
| 25 gal | 3,200 |
| 30 gal | 3,840 |
| 40 gal | 5,120 |
| 50 gal | 6,400 |
| 75 gal | 9,600 |
| 100 gal | 12,800 |
| 250 gal | 32,000 |
| 500 gal | 64,000 |
| 1,000 gal | 128,000 |

## How the conversion works

The relationship is fl oz = gal × 128. Both units measure volume, so the conversion is a fixed factor that never changes. The figure is exact rather than approximate: since the international yard and pound agreement of 1959, an inch is defined as exactly 25.4 millimetres and a pound as exactly 0.45359237 kilograms, and every other imperial and US customary unit here is derived from those two.

> US gallon: US liquid gallon. The imperial gallon is about 20% larger.

## Common questions

### How many US fluid ounces are in one US gallon?

One US gallon equals 128 US fluid ounces. fl oz = gal × 128.

### How do you convert US gallons to US fluid ounces?

Use fl oz = gal × 128. So 10 gal is 1,280 fl oz.

### How many US gallons are in one US fluid ounce?

One US fluid ounce equals 0.0078125 US gallons, which is the reverse of the conversion above.

### Is there more than one kind of US gallon?

US liquid gallon. The imperial gallon is about 20% larger.

## Related pages

- [US fluid ounces to US gallons](https://atoneplace.net/convert/fl-oz-to-gallons/)
- [US gallons to Liters](https://atoneplace.net/convert/gallons-to-liters/)
- [US gallons to Milliliters](https://atoneplace.net/convert/gallons-to-ml/)
- [US gallons to Cubic meters](https://atoneplace.net/convert/gallons-to-cubic-meters/)
- [US gallons to US quarts](https://atoneplace.net/convert/gallons-to-quarts/)
- [US gallons to US pints](https://atoneplace.net/convert/gallons-to-pints/)
- [US gallons to US cups](https://atoneplace.net/convert/gallons-to-cups/)
- [US gallons to Tablespoons](https://atoneplace.net/convert/gallons-to-tablespoons/)
- [US gallons to Teaspoons](https://atoneplace.net/convert/gallons-to-teaspoons/)

## Sources

- Guide for the Use of the International System of Units (SP 811) — NIST (https://www.nist.gov/pml/special-publication-811) [Public domain (US Government)]
- The International System of Units (SI Brochure) — Bureau International des Poids et Mesures (https://www.bipm.org/en/publications/si-brochure)
- Calculated on this page — At One Place (/about/)