US MPG to UK MPG Converter
Convert US miles per gallon to imperial — the same car reads about 20% higher. Results update as you type; exact factors shown.
One miles per US gallon is 1.2009 miles per imperial gallon — see the exact factor, not a rounded rule of thumb.
How the us mpg to uk mpg converter works
Fuel economy is an inverse quantity: lower L/100 km is better, higher mpg is better. mpg (US) = 235.215 / (L/100 km) because a US gallon is 3.785 L and a mile 1.609 km; mpg (UK) = 282.481 / (L/100 km) with the 4.546 L imperial gallon. UK mpg figures are therefore always 20% higher than US mpg for the same car.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common fuel economy conversions
| From | To | Units |
|---|---|---|
| 15 mpg (US) | 18.0142 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 20 mpg (US) | 24.019 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 25 mpg (US) | 30.0237 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 30 mpg (US) | 36.0285 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 35 mpg (US) | 42.0332 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 40 mpg (US) | 48.038 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 45 mpg (US) | 54.0427 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 50 mpg (US) | 60.0475 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 55 mpg (US) | 66.0522 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 60 mpg (US) | 72.057 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 70 mpg (US) | 84.0665 mpg (UK) | miles per US gallon to miles per imperial gallon |
| 100 mpg (US) | 120.095 mpg (UK) | miles per US gallon to miles per imperial gallon |
Units in this converter and their exact factors
| Unit | Symbol | To L/100 km |
|---|---|---|
| litres per 100 km | L/100 km | x |
| kilometres per litre | km/L | 100÷x |
| miles per imperial gallon | mpg (UK) | 282.480936÷x |
| miles per US gallon | mpg (US) | 235.214583÷x |
FAQFrequently asked questions about fuel economy conversion
What is 30 US mpg in UK mpg?
36 UK mpg.
Why the difference?
The imperial gallon holds 4.546 L; the US gallon 3.785 L.
Which figure is on a US window sticker?
US mpg, adjusted downward from the raw test to better match real driving.
What is 50 US mpg in UK mpg?
60 UK mpg.
How do I compare a US and UK review?
Convert both to L/100km, which removes the gallon question entirely.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.