UK Gallons
Abbreviation/Symbol:
gal
g (used only as part of the abbreviation mpg, for miles per gallon)
Unit of:
Worldwide use:
The UK gallon is exactly 4.54609 liters, about 20% bigger than the US gallon.
In the UK the gallon survives in fuel economy, with cars rated in miles per gallon even though petrol is sold by the liter. Nobody quotes miles per liter.
Definition:
The imperial (UK) gallon is officially defined as 4.54609 litres.
Origin:
The gallon is an ancient unit for measuring volume or capacity and has had numerous variations, both geographical and based on what substance was being measured.
In 1824 the imperial gallon was defined in the UK as being the volume of 10 lb of distilled water weighed using a particular method under specific atmospheric conditions. The Weights and Measures Act of 1963 refined the original description as the space occupied by 10 pounds (4.5 kg) of distilled water of density 0.998859 g/ml weighed in air of density 0.001217 g/ml against weights of density 8.136 g/ml.
Since the Weights and Measures Act of 1985, the imperial (UK) gallon has been officially defined as 4.54609 litres.
Common references:
A standard keg of draught beer in the UK contains 11 imperial gallons.
An imperial gallon of petrol (gasoline) will power a typical UK 4-door family car (such as the Vauxhall Astra 1.4i) an average of 46.3 miles (74.5 Km).
An imperial gallon of petrol (gasoline) will power a Porsche 911 (996) an average of 23.9 miles (38.5 Km).
Usage context:
The UK (imperial) gallon is exactly 4.54609 liters, about 20% bigger than the US gallon of 3.785 liters. UK fuel is sold by the liter, but fuel economy is still quoted in miles per imperial gallon, so 40 mpg is about 7.1 liters per 100 kilometers.