Equivalent in Liters:
Table of Contents
The formula
Multiply US gallons by the exact conversion factor:
L = gal × 3.78541
- L — liters, the SI unit for liquid volume.
- gal — US gallons (not UK / imperial gallons).
- 3.78541 — exact NIST value; 1 US gal = 231 in³ = 3.785411784 L.
To reverse (liters to gallons): gal = L ÷ 3.78541. Or use the liters to gallons converter.
Worked example
Default input: 1 US gallon.
- Apply the formula: 1 × 3.78541 = 3.785 liters.
- That is 3 liters plus 785 mL — roughly three and three-quarter standard 1 L bottles.
Gallons to liters conversion table
| US Gallons | Liters |
|---|---|
| 0.5 gal | 1.893 L |
| 1 gal | 3.785 L |
| 2 gal | 7.571 L |
| 3 gal | 11.356 L |
| 4 gal | 15.141 L |
| 5 gal | 18.927 L |
| 10 gal | 37.854 L |
| 15 gal | 56.781 L |
| 20 gal | 75.708 L |
| 25 gal | 94.635 L |
| 50 gal | 189.271 L |
| 100 gal | 378.541 L |
History & standards — the US vs UK gallon gotcha
The gallon has two living definitions, and confusing them leads to ~20% errors:
- US gallon: 3.78541 L = 128 US fl oz = 4 US quarts. Defined in 1836 as exactly 231 cubic inches. Used in the US for fuel, milk, and paint.
- UK / Imperial gallon: 4.54609 L = 160 imperial fl oz = 4 imperial quarts. Defined in 1824 as the volume of 10 pounds of water at 62°F. Used in the UK, Canada (fuel), and some Caribbean nations.
The litre was defined by France in 1795 as 1 dm³. The BIPM today defines it as exactly 0.001 m³. It is the preferred unit for liquids in all SI countries.
Common applications
- Fuel & fuel economy. US pump prices are per gallon; European prices are per liter. A US car that gets 30 mpg uses about 7.84 L/100 km. Knowing the gallon-to-liter ratio is essential for cross-border fuel budgeting.
- Aquariums. Tank sizes are listed in US gallons domestically; equipment from Europe uses liters. A 55-gallon tank holds 208 liters.
- Homebrewing. A standard 5-gallon homebrew batch equals 18.93 liters — fitting neatly in a 20 L fermentation vessel.
- Paint & coatings. US paint is sold in quarts and gallons; coverage rates are often quoted in m²/L. Converting keeps your estimates accurate.
- Water storage. Rain barrels, storage tanks, and water heaters are rated in gallons in the US. International specs use liters.
Limitations & gotchas
- Always specify US or UK gallon. An imperial gallon is 20% larger. Using the wrong factor in fuel calculations can mean buying significantly more or less than you expect.
- Dry gallon. The US dry gallon (4.405 L) is used for dry agricultural commodities (grain, fruit). It is different again from the US liquid gallon (3.785 L). This calculator uses the liquid gallon.
- Canadian fuel. Canada officially uses liters, but some older fuel-economy references quote imperial gallons (4.546 L), not US gallons.
Sources & references
- NIST, “SI Units — Volume.” nist.gov.
- BIPM, “SI Units.” bipm.org.
FAQs
One US gallon equals exactly 3.785411784 liters (commonly rounded to 3.78541 L). This is the definition used in the United States for fuel, milk jugs, and most household containers.
A US gallon = 3.78541 L. A UK (imperial) gallon = 4.54609 L — about 20% larger. If you see fuel economy quoted in “mpg” from a British source, the gallons are imperial. This calculator converts US gallons only; for imperial gallons multiply by 4.54609.
5 US gallons × 3.78541 = 18.927 liters. A standard 5-gallon water cooler jug holds just under 19 liters.
10 US gallons × 3.78541 = 37.854 liters. A 10-gallon aquarium holds roughly 38 liters.
Yes. One US gallon equals 3.785 liters, so a gallon is nearly four times larger than a liter. A UK gallon is even larger at 4.546 liters.
Because they use different gallon sizes. A UK gallon is 4.546 L vs the US gallon of 3.785 L. The same car may achieve 50 UK mpg but only about 42 US mpg — a 20% gap purely from the gallon definition.