Convert US gallons to fluid ounces

1 gal (US)=128fl oz

Use the converter below to change any US gallons value into fluid ounces instantly — with formula, conversion table, and real-world examples.

You have

Equals

128

Conversion formula

Forward

fluid ounces = US gallons × 128

Reverse

US gallons = fluid ounces × 0.007813

Example: 10 gal (US) × 128 = 1,280 fl oz.

About both units

From

US Gallon

gal (US)

The US gallon equals 3.785411784 litres exactly. It is the standard fuel and liquid volume unit in the United States. A typical American car holds 14–18 US gallons of fuel. US fuel economy is quoted in miles per US gallon (mpg).

Real-world: US car tank ≈ 15 gallons (57 L). 1 US gallon of milk is a common grocery size (3.79 L). US paint often sold by the gallon.

Read full us gallon reference →

Fluid Ounce

fl oz

The US fluid ounce equals 29.5735 millilitres — 1/128 of a US gallon. The UK fluid ounce (28.41 ml) is slightly smaller. Used for beverage can sizes in the US, cosmetic product sizes and many US cooking recipes. Do not confuse with the ounce of mass (28.35 g).

Real-world: A US soda can is 12 fl oz (355 ml). A Starbucks Tall is 12 fl oz; Grande is 16; Venti is 20.

Read full fluid ounce reference →

US Gallon to Fluid Ounce conversion table

Common US gallons to fluid ounces values for quick reference.

US Gallon (gal (US))	Fluid Ounce (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
20 gal (US)	2,560 fl oz
50 gal (US)	6,400 fl oz
100 gal (US)	12,800 fl oz
200 gal (US)	25,600 fl oz
500 gal (US)	64,000 fl oz
1,000 gal (US)	128,000 fl oz

Tips & common mistakes

Quick tips

1 US gallon = 3.785 L = 128 US fluid ounces = 4 quarts.
Converting mpg (US) to L/100 km: 235.215 / mpg = L/100 km.
The US gallon is based on the old English Queen Anne wine gallon (1707).

Avoid these

Using UK gallons on a US fuel-economy figure — 30 mpg (US) = 36 mpg (UK).
Confusing US gallon (3.79 L) with UK gallon (4.55 L) — 20% difference.
Using "gallon" without qualifier in cross-Atlantic commerce.

Frequently asked questions

How many fluid ounces in a us gallon?

One us gallon equals 128 fluid ounces.

How do I convert US gallons to fluid ounces?

Multiply the us gallon value by 128 to get the equivalent in fluid ounces.

What is 100 US gallons in fluid ounces?

100 US gallons equals 12,800 fluid ounces.

Is a us gallon bigger than a fluid ounce?

Yes. 1 us gallon equals 128 fluid ounces, so one us gallon is larger.

How to convert US gallons to fluid ounces without a calculator?

Multiply by 128 for a quick estimate; use a calculator for precise results.

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