How to convert Miles per US gallon to miles per Imperial gallon
mpg (UK) = mpg (US) × 1.20094992550485
Multiply the mpg (US) reading by 1.20094992550485. Both sides measure distance per fuel volume, so this is a direct scale conversion. US mpg uses a 3.785411784 L gallon. Imperial mpg uses a 4.54609 L gallon.
Worked examples
30 mpg (US) ≈ 36.02849777 mpg (UK)
30 × 1.20094992550485 ≈ 36.02849777
50 mpg (US) ≈ 60.04749628 mpg (UK)
50 × 1.20094992550485 ≈ 60.04749628
Frequently asked questions
Why can a fuel-economy reading change without using less fuel?
Distance per litre and distance per gallon use different fuel-volume units. US and Imperial gallons also differ. A changed numerical reading after conversion describes the same economy.