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Gallon Calculator

Convert gallon between units instantly. Includes conversion tables, common equivalents, and calculation formulas. Enter your values for instant results.

Reviewed by Manoj Kumar, Mathematics Educator

Reviewed by Manoj Kumar, Mathematics Educator

Formula

1 US gallon = 231 in3 = 3.78541 L = 4 qt = 8 pt = 16 cups = 128 fl oz

The US gallon is defined as exactly 231 cubic inches. For container capacity, calculate the volume in cubic inches (length x width x height for rectangular containers) and divide by 231. All sub-units follow a doubling pattern: 1 gallon = 4 quarts, 1 quart = 2 pints, 1 pint = 2 cups, 1 cup = 8 fluid ounces.

Worked Examples

Example 1: Aquarium Volume

Problem:Calculate the gallon capacity of a fish tank measuring 36 x 18 x 16 inches.

Solution:Volume = L x W x H\nVolume = 36 x 18 x 16 = 10,368 cubic inches\nGallons = 10,368 / 231 = 44.88 US gallons\nLiters = 44.88 x 3.78541 = 169.9 L\nWeight of water = 44.88 x 8.345 = 374.5 lbs

Result:44.88 US gallons = 169.9 liters

Example 2: Recipe Scaling

Problem:Convert 2.5 gallons to cups and fluid ounces.

Solution:Cups = 2.5 x 16 = 40 cups\nFluid ounces = 2.5 x 128 = 320 fl oz\nQuarts = 2.5 x 4 = 10 quarts\nLiters = 2.5 x 3.78541 = 9.464 L

Result:2.5 gallons = 40 cups = 320 fl oz

Frequently Asked Questions

How many liters are in a gallon?

One US gallon equals exactly 3.78541 liters. One US gallon is also defined as 231 cubic inches or 128 US fluid ounces. The imperial (UK) gallon is larger at 4.54609 liters. The US gallon originated from the English wine gallon of 231 cubic inches, while the imperial gallon was defined in 1824 as the volume occupied by 10 pounds of water at a specific temperature. For everyday use, remember that 1 gallon is approximately 3.8 liters.

How much does a gallon of water weigh?

One US gallon of water weighs approximately 8.345 pounds (3.785 kilograms) at room temperature (about 62 degrees Fahrenheit or 17 degrees Celsius). The exact weight varies slightly with temperature because water density changes. At its densest point (39.2 degrees F or 4 degrees C), a gallon weighs about 8.35 pounds. The old saying goes, a pint is a pound the world around, which is a reasonable approximation since a pint of water weighs about 1.04 pounds.

References

Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy