Fuel cost calculator
Work out what a journey costs in petrol or diesel, and split it between the people travelling.
Uses the average UK pump prices that DESNZ publishes each week. This week, beginning 9 November 2026: petrol 170.71p, diesel 198.19p a litre.
Result
100 miles costs £17.25 in petrol at this week's UK average of 170.71p a litre.
in petrol, to the nearest penny
| Fuel used | 10.1 litres |
|---|---|
| Cost a mile | 17.2p |
Show the workings
| Step | Sum | Answer |
|---|---|---|
| Fuel used | 100 miles ÷ 45 mpg × 4.54609 litres a gallon | 10.102 litres |
| Fuel cost | 10.1 litres × 170.71p | £17.25 |
What this leaves out or assumes
- Uses the miles per gallon you enter. Real fuel use changes with speed, traffic, load and the weather.
Where the figures come from
- Average UK pump price of unleaded petrol: 170.71p a litre. Source: DESNZ: Weekly road fuel prices. Checked 13 November 2026.
- One UK gallon, in litres: 4.54609 litres. Source: Weights and Measures Act 1985, Schedule 1. Checked 13 November 2026.
Fuel cost of 100 miles
| Miles per gallon | Petrol | Diesel |
|---|---|---|
| 30 mpg | £25.87 | £30.03 |
| 40 mpg | £19.40 | £22.52 |
| 50 mpg | £15.52 | £18.02 |
| 60 mpg | £12.93 | £15.02 |
The sum
Miles divided by miles per gallon gives the gallons you use. A UK gallon is 4.54609 litres, so multiply by that for litres, then by the price a litre. 100 miles at 50 mpg is 2 gallons, or 9.09 litres.
If your car shows litres per 100 km, the calculator turns it into miles per gallon for you. UK gallons are bigger than US gallons, so an mpg figure from a US website will look lower.
The weekly prices are DESNZ's average UK pump prices. Prices vary from one filling station to another: choose "the price at my pump" to use your own.