How to Convert Gallons to Liters
Volume · Last updated: July 2025
A “gallon” is not universal. The US gallon is 231 cubic inches (≈ 3.785411784 L). The UK imperial gallon is about 4.54609 L—roughly 20% larger. Always know which gallon you start with.
The formulas
Liters = US gallons × 3.78541
Liters = UK gallons × 4.54609
US gallons = liters ÷ 3.78541
Side-by-side comparison
| From | To |
|---|---|
| 1 US gal | 3.785 L |
| 1 UK gal | 4.546 L |
| 5 US gal | 18.927 L |
| 1 L | 0.264 US gal |
| 1 L | 0.220 UK gal |
Why the confusion matters
Fuel economy
US miles per gallon (mpg) uses the US gallon. UK mpg uses the imperial gallon, so the same numeric mpg means better efficiency in the UK. When comparing international ratings, convert to L/100 km.
Recipes and beverages
Old UK recipes may mean imperial gallons or pints. US recipes use US customary cups and gallons. Imported wine and soda labels often use liters.
Industrial and automotive fluids
Coolant, oil, and chemical drums may be labeled in liters globally while US retail still uses quarts and gallons.
See our dedicated guide: US vs UK units.
Common mistakes
- Assuming one conversion factor for all “gallons.”
- Confusing fluid ounces (volume) with ounces (mass).
- Using dry gallons (US dry measure, ~4.404 L)—rare today but still in some agricultural contexts.
References
Specify US or UK gallon in tounits.com when you convert — try 2 us gallon or 10 liter.