Global Fuel CalculatorUS MPG to UK MPG Converter
Ever seen the same car rated at 40 MPG on an American site and something noticeably higher on a British one? Nobody is fudging the numbers. The gallons are different. This converter turns a US MPG figure into the UK (imperial) figure for the same car, using the exact gallon definitions instead of a rounded rule of thumb.
The gap is big enough to matter. An imperial gallon holds about 20% more fuel than a US gallon, so the UK number is always the larger one for identical consumption. Type a value above and the result also shows L/100km and km/L, which you can check against a European or Asian spec sheet.
US MPG to UK MPG Converter
The conversion formula
UK MPG = US MPG × 1.20095
Worked example: 30 MPG (US) = 36.03 MPG (imp)
Need it the other way round? Use the UK MPG to US MPG Converter.
US MPG to UK MPG conversion table
| MPG (US) | L/100km | km/L | MPG (imp) |
|---|---|---|---|
| 20 | 11.76 | 8.50 | 24.02 |
| 25 | 9.41 | 10.63 | 30.02 |
| 30 | 7.84 | 12.75 | 36.03 |
| 35 | 6.72 | 14.88 | 42.03 |
| 40 | 5.88 | 17.01 | 48.04 |
| 45 | 5.23 | 19.13 | 54.04 |
| 50 | 4.70 | 21.26 | 60.05 |
How to use the US MPG to UK MPG Converter
- Enter your value. Type the figure you want to convert, in MPG (US).
- Check the units. Make sure "From" shows MPG (US) and "To" shows MPG (imperial). Press Swap to reverse them.
- Read the result. The answer appears straight away, worked out as UK MPG = US MPG × 1.20095.
- Check common values. Compare against the conversion table below if you want to sanity-check a figure.
Common questions
How do I convert US MPG to UK MPG?
Multiply the US figure by 1.2009. Thirty US MPG becomes about 36.03 UK MPG. The factor is simply the imperial gallon (4.54609 litres) divided by the US gallon (3.785411784 litres).
Why is the UK number always bigger?
Because the UK gallon is the bigger measuring cup. A car that covers 30 miles on one US gallon covers the same 30 miles on less than one imperial gallon, so per imperial gallon it goes about 36 miles. The car hasn't changed, only the unit.
Which figure should I quote when selling or comparing a car internationally?
Quote the figure used in the buyer's market and name the gallon. "30 MPG (US)" and "36 MPG (UK)" describe the same car, but an unlabelled "30 MPG" will be read the wrong way by a large share of your audience.
Does the conversion work for real-world figures as well as official ones?
Yes. It only changes the unit, so it's equally valid for a manufacturer's rating and for the economy you measured yourself at the pump.
Is there a way to avoid the gallon problem altogether?
Use L/100km or km/L. Neither depends on a gallon, which makes them the cleanest yardstick when you're weighing up cars from different countries. This page shows both next to every result.