Fuel Cost · UK 2025
20 MPG Fuel Cost Calculator — Annual UK Driving Cost
At 20 miles per gallon, UK petrol at 145p per litre works out at roughly 33.0p per mile, and diesel at 148p per litre is about 33.6p per mile. Over 10,000 miles, that is £3,295.85 a year on petrol.
20 mpg is typical of large SUVs, performance cars or older petrol vehicles. Fuel will be one of the bigger items in your running costs; combining trips, lower-speed cruising and maintaining correct tyre pressures can claw back a few percent. Switching to a smaller petrol or hybrid often pays back quickly at this efficiency level.
Annual fuel cost at 20 mpg
| Annual miles | Petrol (145p/L) | Diesel (148p/L) |
|---|---|---|
| 5,000 miles | £1,647.93 | £1,682.02 |
| 7,500 miles | £2,471.89 | £2,523.03 |
| 10,000 miles | £3,295.85 | £3,364.04 |
| 12,500 miles | £4,119.81 | £4,205.05 |
| 15,000 miles | £4,943.78 | £5,046.06 |
Based on UK imperial gallons (4.546 litres/gallon). Pump prices fluctuate weekly — check the latest with the RAC Fuel Watch or BEIS weekly price data.
How the calculation works
UK MPG is based on the imperial gallon, which equals 4.546 litres. Cost per mile is calculated as:
At 20 mpg you burn 0.227 litres per mile. Multiply by your local pump price to get the exact cost per mile for your area.