How many liters is 1 imperial gallon?

One imperial gallon = 4.54609 liters.

How does the imperial gallon compare to the US gallon?

An imperial gallon is 4.546 L; a US gallon is 3.785 L. The imperial gallon is about 20% larger.

Why does UK mpg appear better than US mpg for the same car?

Because UK fuel economy uses the larger imperial gallon (4.546 L vs 3.785 L), a car achieving 40 UK mpg actually consumes more fuel per km than a US car rated at 40 US mpg.

Imperial Gallons to Liters Converter

Convert imperial (UK) gallons to liters for fuel comparison, historical recipes, and understanding British and Commonwealth measurements. The imperial gallon is about 20% larger than the US gallon.

Formula

Multiply imperial gallons by 4.54609 to get liters. To reverse, divide liters by 4.54609 to get imperial gallons.

Quick reference

Imperial Gallon (imp_gal)	Liter (L)
1	4.54609
2	9.09218
5	22.73045
10	45.4609
15	68.19135
20	90.9218
30	136.3827
40	181.8436
50	227.3045
100	454.609

About these units

Imperial Gallon

The imperial gallon (277.42 cubic inches) was standardized in the UK in 1824 as the volume of 10 pounds of water at 62°F. It is still used in the UK for fuel tank capacity and in some Commonwealth countries for road fuel economy.

Liter

The liter is the metric unit for liquid volume. UK fuel economy (miles per imperial gallon) must be converted to liters for comparison with European L/100km figures.

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