ConverterHub

US to UK MPG Converter

Enter US mpg to convert to UK mpg and L/100km.

How it is calculated

You enter fuel economy in US miles per gallon. The tool computes UK mpg = US mpg × 1.20095 and L/100 km = 235.214583 ÷ US mpg. The factor 1.20095 is the ratio of the imperial gallon (4.54609 litres) to the US gallon (3.78541 litres); the constant 235.214583 is the number of litres per 100 km that corresponds to 1 US mpg. Both outputs are rounded to two decimals. The conversion works one way only, from US mpg to the other two figures: to start from UK mpg you would divide by 1.20095 yourself. The value must be above zero, because zero economy has no meaningful conversion. The result is a unit change, not a fuel-use estimate for any trip.

Worked example

A car is rated at 30 US mpg. UK mpg = 30 × 1.20095 = 36.0285, shown as 36.03. In litres per 100 km, 235.214583 ÷ 30 = 7.8405, shown as 7.84 L/100km. The same car looks about 20% more economical in imperial gallons only because the gallon is bigger, not because it burns less fuel.

Try this example →

Common mistakes

  • Typing a UK mpg figure into the US field. The input is US mpg, so a UK value would be inflated by about 20% in the results.
  • Believing the UK number means a more efficient car. The vehicle is identical; the imperial gallon is simply larger.
  • Comparing L/100 km directly with mpg as if higher were better in both. Lower L/100 km is better, while higher mpg is better.
  • Averaging mpg values across trips or cars. Fuel economy should be averaged in L/100 km (consumption), not in mpg.
  • Assuming the rating applies to your driving. Test-cycle figures and real-world consumption differ, and the converter changes units only.

About this calculator

US and UK "miles per gallon" are not the same unit because the US gallon (3.785 litres) and the imperial gallon (4.546 litres) differ by about 20% — the imperial gallon is larger, so for the same car, the UK mpg figure is always higher than the US mpg figure (roughly US mpg × 1.201 = UK mpg). The metric equivalent, litres per 100 km, sidesteps the ambiguity entirely and is the standard fuel-economy figure across the EU and most of the world outside the US and UK.

Car shoppers comparing a US-market review to a UK-market review of the same model, and auto journalists and importers converting spec sheets between the two markets, rely on this converter to avoid misreading two very different-looking numbers as directly comparable.

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