Unit Conversions
Liters vs Gallons: Understanding Liquid Measurements
Convert between liters and gallons confidently. Includes US vs UK gallon differences, fuel economy comparisons, and everyday examples.
Liters and gallons both measure volume, but the gallon comes in two different sizes — US and Imperial (UK). This causes confusion whenever American and British measurements appear together, especially for fuel economy and large-volume containers.
The Conversion Factors
- 1 US gallon = 3.785 liters
- 1 UK (Imperial) gallon = 4.546 liters
- 1 liter = 0.264 US gallons
- 1 liter = 0.220 UK gallons
Why Two Types of Gallon?
The US gallon descends from the Queen Anne wine gallon (231 cubic inches), standardized in 1707. The Imperial gallon was standardized later in 1824 to be the volume of 10 pounds of water at a specific temperature. The two systems diverged — and never reunited.
Fuel Economy: MPG vs L/100km
Fuel economy is reported differently in different countries. The US uses miles per gallon (MPG). Canada and Europe use liters per 100 kilometers (L/100km). To convert: L/100km = 235.21 ÷ US MPG. A car getting 30 US MPG gets approximately 7.84 L/100km.
Common Reference Points
- 1 liter water bottle ≈ 0.26 US gallons
- A standard US 'fifth' of spirits = 750 mL = 0.2 US gallons
- 5-gallon water cooler jug ≈ 18.9 liters
- Standard US gas tank (≈15 gallons) ≈ 56.8 liters