Convert MPG (UK) to MPG (US) instantly — enter a value in either field.
| MPG (UK) (mpg (UK)) | MPG (US) (mpg (US)) |
|---|---|
| 18 mpg (UK) | 15 mpg (US) |
| 24 mpg (UK) | 20 mpg (US) |
| 30 mpg (UK) | 25 mpg (US) |
| 36 mpg (UK) | 30 mpg (US) |
| 42 mpg (UK) | 35 mpg (US) |
| 48 mpg (UK) | 40 mpg (US) |
| 54 mpg (UK) | 45 mpg (US) |
| 60 mpg (UK) | 50 mpg (US) |
| 66 mpg (UK) | 55 mpg (US) |
| 72 mpg (UK) | 60 mpg (US) |
Example: 40 mpg (UK) → 40 × 0.832674 = 33.3 mpg (US)
Imperial mpg is larger than US mpg for the same car because the UK gallon (4.54609 L) is larger than the US gallon (3.785411784 L). Converting from UK to US mpg means the number goes down: mpg (US) = mpg (UK) × 0.832674.
A 40 UK mpg car gets 33.3 US mpg. A 50 UK mpg car is actually 41.6 US mpg. This difference trips up buyers comparing cars across markets: a British review saying “50 mpg” and an American review saying “41 mpg” can describe the exact same vehicle with the same fuel consumption.
Since 2011, UK car fuel economy must be stated in L/100km as the primary figure. The EU and UK regulatory tests (NEDC, then WLTP) produce L/100km figures that convert unambiguously to mpg in either gallon standard. When in doubt, use L/100km as the common reference.
The US gallon (3.785 L) is smaller than the UK imperial gallon (4.546 L). Fewer miles fit into each smaller US gallon, so the US mpg number is always lower for the same car.
50 × 0.832674 = 41.6 mpg US. The factor 0.832674 is 3.785411784 ÷ 4.54609.
A British review saying “50 mpg” and an American review saying “42 mpg” might describe identical vehicles — the difference is entirely the gallon definition.