Gallon Calculator
Convert gallon between units instantly. Includes conversion tables, common equivalents, and calculation formulas. Enter your values for instant results.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator
Gallon Calculator
Calculator
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Formula: 1 US gallon = 231 in3 = 3.78541 L = 4 qt = 8 pt = 16 cups = 128 fl oz
Worked example — 44.88 US gallons = 169.9 liters
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 Volume = 36 x 18 x 16 = 10,368 cubic inches Gallons = 10,368 / 231 = 44.88 US gallons Liters = 44.88 x 3.78541 = 169.9 L Weight 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 Fluid ounces = 2.5 x 128 = 320 fl oz Quarts = 2.5 x 4 = 10 quarts Liters = 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 do I calculate how many gallons a container holds?
For a rectangular container, multiply length by width by height (all in inches) to get cubic inches, then divide by 231 to get US gallons. For example, a container measuring 24 x 12 x 12 inches has a volume of 3,456 cubic inches, which is 3,456 / 231 = 14.96 gallons. For cylindrical containers, calculate cubic inches using pi x radius-squared x height, then divide by 231. Always use interior dimensions for accurate capacity calculations.
What is the relationship between gallons, quarts, pints, and cups?
The US liquid volume system follows a clear hierarchy: 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces. Each step doubles: 1 quart = 2 pints, 1 pint = 2 cups, 1 cup = 8 fluid ounces. One fluid ounce equals 2 tablespoons, and 1 tablespoon equals 3 teaspoons. This system makes it easy to scale recipes up or down. Memorize the key conversion: 1 gallon = 16 cups, and you can derive all other relationships.
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 for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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