Why are UK and US mpg different?

A UK (imperial) gallon is 4.54609 litres while a US gallon is 3.785412 litres. Because the UK gallon is larger, the same car shows a higher mpg figure in the UK.

How do I convert UK mpg to US mpg?

Divide the UK figure by 1.200950 (the ratio of gallon sizes). To convert US mpg to UK mpg, multiply by 1.200950.

Does this tool use the internet?

No — every conversion runs locally in your browser and nothing is uploaded.

Miles per Gallon UK to US Converter

Convert fuel economy between UK and US miles per gallon.

UK to US miles-per-gallon converter

Fuel economy in miles per gallon depends on which gallon you use. The imperial (UK) gallon is 4.54609 litres while the US gallon is 3.785412 litres, so the same real economy reads higher in UK mpg: US mpg = UK mpg ÷ 1.200950.

Enter a value in either field and the other updates instantly — all in your browser, with no data sent to a server.