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US Gallon

Also called: gallon, US liquid gallon, gal

Definition: The US liquid gallon is a customary volume unit of 231 cubic inches, equal to 3.785412 liters, 128 US fluid ounces, 4 quarts, 8 pints or 16 cups.

Updated October 29, 2026 · How we check facts

The US gallon (gal) is the standard liquid gallon of the US customary units. NIST lists it as 3.785412 liters. Its definition in cubic inches is 231 in³, and 231 × 2.54³ cm³ equals 3,785.41 mL. It splits into 4 quarts, 8 pints, 16 cups or 128 US fluid ounces.

Conversion

L = gal × 3.785412
gal = L ÷ 3.785412
fl oz = gal × 128

Example

A 5 gal container holds 5 × 3.785412 = 18.93 L and 5 × 128 = 640 fl oz. A 10 L tank is 10 ÷ 3.785412 = 2.64 gal.

US vs imperial

The imperial gallon is a different unit, exactly 4.54609 L, 20.1% larger than the US gallon (4.54609 ÷ 3.785412 = 1.2009). Check which one a source means before converting.

The guides how many liters in a gallon and how many ounces in a gallon have full charts; gallons to liters converts any value.

Calculate it

Free toolVolume CalculatorVolume of any common solid, with the formula shown.

Guides that explain it

Related terms

Imperial GallonThe imperial gallon, used in the UK and in Canadian measures, is exactly 4.54609 liters, about 20% larger than the US gallon (3.785412 L).Liter (L)The liter is a metric unit of volume equal to one thousandth of a cubic meter (1,000 mL); about 33.81 US fluid ounces and 0.2642 US gallons.US Customary UnitsUS customary units are the inch, foot, mile, ounce, pound, cup and gallon used for everyday measures in the United States; each is defined by an exact or fixed value in SI units.Fluid Ounce (fl oz)A fluid ounce is a unit of volume; one US fluid ounce is 29.57353 milliliters, and 8 of them make a US cup. It is not the same as the ounce used to weigh things.Gram (g)The gram is a metric unit of mass equal to one thousandth of a kilogram, the SI base unit of mass; about 0.03527 ounces.Inch (in)The inch is a unit of length equal to exactly 2.54 centimeters (0.0254 m); 12 inches make a foot and 36 make a yard; a meter is 39.37 inches.International FootThe international foot is the standard foot of 0.3048 meters exactly; it replaced the US survey foot for all uses from 1 January 2023, apart from historic data.Kilogram (kg)The kilogram is the SI base unit of mass, equal to 1,000 grams and about 2.2046 pounds; it is the only base unit whose name carries a prefix.

Sources

  1. NIST Guide to the SI (SP 811), Appendix B.8 — Factors for Units Listed Alphabetically