Convert MPG (US) to MPG (UK)
MPG (US) to MPG (UK) is the conversion you need when a car's fuel economy is quoted in US miles per gallon but you're used to the UK figure — or the other way around. One US mpg is approximately 1.2009499 UK mpg, so the UK number always comes out higher for the very same car. That doesn't mean it goes farther — it's just that the imperial gallon is bigger.
Miles per gallon (US) to Miles per gallon (UK) conversion table
| Miles per gallon (US) (mpg (US)) | Miles per gallon (UK) (mpg (UK)) |
|---|---|
| 1 | 1.20095 |
| 2 | 2.4019 |
| 3 | 3.60285 |
| 5 | 6.00475 |
| 10 | 12.009499 |
| 20 | 24.018999 |
| 50 | 60.047496 |
| 100 | 120.094993 |
| 500 | 600.474963 |
| 1,000 | 1,200.949926 |
The formula
To convert MPG (US) to MPG (UK), multiply the US figure by 1.2009499:
mpg (UK) = mpg (US) × 1.2009499
A worked example
Say a car is rated at 30 mpg in US figures and you want the UK number:
30 × 1.2009499 = 36.03 mpg (UK)
So 30 US mpg is about 36.03 UK mpg — the same car, just measured against the larger UK gallon.
Why it's an approximation
The factor 1.2009499 is a rounded value. It comes from the gap between the two gallons: the imperial (UK) gallon is about 20% larger than the US gallon. Since miles per gallon means the miles you get from one gallon, a bigger gallon gives you a bigger number for the exact same car. That's why the UK figure looks better even though nothing about the car changed. And because the two gallon sizes don't divide evenly, the factor stays approximate.
When you'll use it
Comparing a car's fuel economy from a UK review or brochure against US figures, or making sense of a spec sheet that quotes mpg without saying which gallon it means. Watch the trap: a "higher" UK mpg isn't a more efficient car — it's the bigger gallon talking.
Frequently asked questions
Why is the UK mpg number higher than the US one?
Because the imperial (UK) gallon is about 20% larger than the US gallon. A gallon of fuel goes further when the gallon itself holds more, so the same car scores a higher mpg on UK figures — roughly 1.2009499 times the US number. It's not more efficient, it's measured against a bigger gallon.
How many UK mpg is 30 US mpg?
About 36.03 UK mpg. Multiply 30 by 1.2009499 and you get 36.03. It's the identical car burning the identical fuel — only the size of the gallon changed.
Is the MPG (US) to MPG (UK) conversion exact?
No. The factor 1.2009499 is rounded, because the US and imperial gallons don't divide evenly. It's precise enough for comparing car figures, but the digits carry on past where the number is cut off.