Gallons To Fluid Ounces Conversion (gal To Fl Oz) - Inch Calculator

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• Gallons to Fluid Ounces Converter
• How to Convert Gallons to Fluid Ounces
• How Many Fluid Ounces Are in a Gallon?
• What Is a Gallon?
• What Is a Fluid Ounce?
• Gallon to Fluid Ounce Conversion Table
• References

Person Icon By Joe Sexton

Joe is the creator of Inch Calculator and has over 20 years of experience in engineering and construction. He holds several degrees and certifications.

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Sexton, J. (n.d.). Gallons to Fluid Ounces Converter. Inch Calculator. Retrieved January 1, 2026, from https://www.inchcalculator.com/convert/gallon-to-fluid-ounce/

How to Convert Gallons to Fluid Ounces

To convert a measurement in gallons to a measurement in 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:

fluid ounces = gallons × 128

The volume in fluid ounces is equal to the volume in gallons multiplied by 128.

For example, here's how to convert 5 gallons to fluid ounces using the formula above.

fluid ounces = (5 gal × 128) = 640 fl oz

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.

1 gal = 128 fl oz

Gallons and fluid ounces are both units used to measure volume. Keep reading to learn more about each unit of measure.

What Is a Gallon?

The US liquid gallon is a unit of fluid volume equal to four quarts, eight pints, or sixteen cups.[1] The US liquid gallon should not be confused with the US dry gallon or the imperial gallon, which are different units of measure.

The gallon is a US customary unit of volume. Gallons can be abbreviated as gal; for example, 1 gallon can be written as 1 gal.

Learn more about gallons.

What Is a Fluid Ounce?

The US fluid ounce is a unit of volume equal to 1/16 of a pint or 1/8 of a cup. The fluid ounce is sometimes referred to as just an "ounce" but should not be confused with the unit of weight. One fluid ounce is equal to approximately 29.5735 milliliters, but in nutrition labeling, one fluid ounce is rounded to exactly 30 milliliters.[2]

The fluid ounce is a US customary unit of volume. Fluid ounces can be abbreviated as fl oz, and are also sometimes abbreviated as oz fl. For example, 1 fluid ounce can be written as 1 fl oz or 1 oz fl.

Learn more about fluid ounces.

Gallon to Fluid Ounce Conversion Table

Table showing various gallon measurements converted to fluid ounces.

Gallons	Fluid Ounces
1 gal	128 fl oz
2 gal	256 fl oz
3 gal	384 fl oz
4 gal	512 fl oz
5 gal	640 fl oz
6 gal	768 fl oz
7 gal	896 fl oz
8 gal	1,024 fl oz
9 gal	1,152 fl oz
10 gal	1,280 fl oz
11 gal	1,408 fl oz
12 gal	1,536 fl oz
13 gal	1,664 fl oz
14 gal	1,792 fl oz
15 gal	1,920 fl oz
16 gal	2,048 fl oz
17 gal	2,176 fl oz
18 gal	2,304 fl oz
19 gal	2,432 fl oz
20 gal	2,560 fl oz
21 gal	2,688 fl oz
22 gal	2,816 fl oz
23 gal	2,944 fl oz
24 gal	3,072 fl oz
25 gal	3,200 fl oz
26 gal	3,328 fl oz
27 gal	3,456 fl oz
28 gal	3,584 fl oz
29 gal	3,712 fl oz
30 gal	3,840 fl oz
31 gal	3,968 fl oz
32 gal	4,096 fl oz
33 gal	4,224 fl oz
34 gal	4,352 fl oz
35 gal	4,480 fl oz
36 gal	4,608 fl oz
37 gal	4,736 fl oz
38 gal	4,864 fl oz
39 gal	4,992 fl oz
40 gal	5,120 fl oz

References

1. National Institute of Standards and Technology, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, Handbook 44 - 2019 Edition, https://nvlpubs.nist.gov/nistpubs/hb/2019/NIST.HB.44-2019.pdf
2. U.S. Food & Drug Administration, Guidance for Industry: Guidelines for Determining Metric Equivalents of Household Measures, https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-guidelines-determining-metric-equivalents-household-measures

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