Gallons to Liters Converter
Free gallons to liters converter — US gallons to litres with the exact factor 3.785411784, plus the UK imperial value. No signup.
About the Gallons to Liters Converter
Convert gallons to litres using the exact US definition: 1 US gallon = 3.785411784 L. Enter gallons and get litres instantly — with the UK imperial equivalent (1 imperial gallon = 4.54609 L) shown alongside, since the two gallons differ by about 20%.
Fuel is the everyday driver for this conversion: US pump prices and car tank sizes are in gallons, while most of the world sells fuel by the litre. A 15-gallon tank holds 56.8 L; 10 gallons is 37.85 L. It also appears with aquariums, pools, paint cans, water heaters and milk jugs.
For fuel economy, remember the units invert: converting miles-per-gallon to litres-per-100 km is not a simple multiplication — but converting the raw volumes, as this tool does, uses the exact factor with no rounding.
How to Use the Gallons to Liters Converter
- 1Enter a volume in US gallons — for example 15 for a fuel tank.
- 2Read the litres result instantly (15 gal = 56.78 L), with the UK gallon value below.
- 3Type litres instead to convert back to gallons.
- 4Check the table for common volumes from 1 to 100 gallons.
Frequently Asked Questions
How many liters are in a gallon?
One US gallon is 3.785411784 litres exactly. One UK (imperial) gallon is larger: 4.54609 litres. This converter uses the US gallon, the one on American fuel pumps and in US recipes.
How many liters is 5 gallons?
5 US gallons is 18.93 litres — the size of a typical water-cooler jug. 5 imperial gallons would be 22.73 litres.
How many liters is a 10 gallon tank?
A 10 US-gallon tank holds 37.85 litres. Common aquarium sizes: 20 gal = 75.7 L, 55 gal = 208.2 L.
Why are US and UK gallons different?
The US kept the old English wine gallon (231 cubic inches = 3.785 L), while Britain redefined its gallon in 1824 as the volume of 10 pounds of water (4.546 L). An imperial gallon is about 20% larger, so always check which one a figure uses.
How do I convert gallons to liters in my head?
Multiply US gallons by 3.8 (or by 4 and knock off 5%). 12 gallons × 3.8 ≈ 45.6 L, very close to the exact 45.42 L. For imperial gallons multiply by 4.5.