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.
Australia is fully metric under the National Measurement Act 1960; imperial units appear only in trade with the US and in older documents.
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 Measurement Institute (NMI) — Australia's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.