Gallon Calculator
Convert between US gallons, UK gallons, litres, pints, quarts, cups, fluid ounces, cubic feet, and cubic metres.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
1 US Gallons (gal) = 3.7854 Litres (L)
This tool provides general unit conversions for everyday and educational use. For regulated, legal, or scientific applications, verify conversion factors against the applicable official standard.
About the Gallon Calculator
The gallon calculator converts between US gallons, UK (imperial) gallons, litres, quarts, pints, cups, fluid ounces and cubic units. The US gallon is 3.785 litres and the imperial gallon is 4.546 litres — about 20% larger — so it matters which one a source uses. The tool handles both and shows the full set of equivalents.
How to use it
- 1Type the value you want to convert.
- 2Choose the unit you are converting from and the unit you want (for example US gallons to litres).
- 3The result updates as you type; use the swap button to reverse the direction.
- 4Copy or share the result with the buttons below it.
Worked example
5 US gallons × 3.785 = 18.93 litres. One imperial gallon equals about 1.2 US gallons.
How it works
US vs UK Gallon
1 US gallon = 3.78541 L; 1 UK (imperial) gallon = 4.54609 L. The two differ by about 20%.
Gallon hierarchy
- 1 US gallon = 4 quarts = 8 pints = 16 cups = 128 fl oz
Common use cases
- Converting fuel volumes and prices
- Sizing fish tanks, water butts and containers
- Comparing US and UK recipe quantities
Frequently asked questions
A:The US gallon is based on the wine gallon historically used in England, while the UK imperial gallon was redefined in 1824 to equal 10 pounds of water.
A:1 US gallon = 3.78541 L; 1 UK gallon = 4.54609 L.
Reviewed for accuracy · Last updated October 7, 2026
Conversion factors are based on internationally defined SI units and standard metric/imperial equivalence tables.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
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