Gallon Calculator
Convert gallon between units instantly. Includes conversion tables, common equivalents, and calculation formulas. Enter your values for instant results.
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.
Is Gallon Calculator free to use?
Yes, completely free with no sign-up required. All calculators on NovaCalculator are free to use without registration, subscription, or payment.
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You can bookmark the calculator page in your browser. Many calculators also display a shareable result summary you can copy. The page URL stays the same so returning to it will bring you back to the same tool.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.
Can I use Gallon Calculator on a mobile device?
Yes. All calculators on NovaCalculator are fully responsive and work on smartphones, tablets, and desktops. The layout adapts automatically to your screen size.