How to work out your fuel cost per mile
A simple formula to turn the price per litre and your MPG into pence per mile, with worked examples for petrol and diesel cars.
Fuel prices are in pence per litre but car economy is in miles per gallon. Here is how to combine them.
The formula
Cost per mile = price per litre × 4.546 ÷ MPG (an imperial gallon is 4.546 litres).
Examples
| Price | MPG | Cost per mile |
|---|---|---|
| 172p (petrol) | 40 | 19.5p |
| 172p (petrol) | 55 | 14.2p |
| 195p (diesel) | 50 | 17.7p |
| 195p (diesel) | 65 | 13.6p |
Cost of a trip
Multiply the cost per mile by the distance. At 19.5p a mile, a 200-mile journey costs about £39. To find your real MPG, fill the tank, note the mileage, drive, fill it again and divide the miles driven by the gallons added (litres ÷ 4.546).
Use today’s prices from the UK home page in the formula.
Frequently asked questions
How many litres in a gallon?
An imperial gallon is 4.546 litres. US gallons are smaller (3.785 litres), so US MPG figures are not the same as UK ones.