Journey fuel cost calculator
At 174.3p a litre, a petrol car doing 45 mpg costs about £17.61 in fuel per 100 miles.
- Each person pays
- £17.61
- Per mile
- 17.6p
- Fuel used
- 10.1 litres
- Total distance
- 100 miles
100 miles at 45 mpg, with fuel at 174.3p a litre.
Fuel only. Parking, tolls and wear on the car are extra.
Fuel cost per 100 miles
At UK average prices for the week ending 11 October 2026.
| Fuel economy | Petrol (174.3p) | Diesel (199.4p) |
|---|---|---|
| 30 mpg | £26.41 | £30.22 |
| 35 mpg | £22.64 | £25.90 |
| 40 mpg | £19.81 | £22.66 |
| 45 mpg | £17.61 | £20.14 |
| 50 mpg | £15.85 | £18.13 |
| 55 mpg | £14.41 | £16.48 |
| 60 mpg | £13.21 | £15.11 |
How we calculate this
UK mpg uses the imperial gallon, which is 4.546 litres. We divide the distance by your mpg to get gallons, convert to litres, and multiply by the price per litre.
Default prices are UK averages from the government’s Fuel Finder data for the week ending 11 October 2026. Prices change every week and vary a lot between garages, so use the price you actually pay.
Questions people ask
How do I work out the fuel cost of a journey?
Divide the miles by your car’s mpg to get gallons, multiply by 4.546 to get litres, then multiply by the price per litre. The calculator does this for you.
How much does 100 miles cost in petrol?
At 174.3p a litre, about £19.81 in a car doing 40 mpg, or £14.41 at 55 mpg.
How do I find my car’s real mpg?
Most cars show average mpg on the dashboard. For a more accurate figure, fill the tank, reset the trip counter, and at the next fill-up divide the miles by the litres added, then multiply by 4.546.
How should passengers split fuel costs?
Splitting the fuel cost equally is common. HMRC’s approved mileage rates also give a guide for work journeys, and our mileage allowance calculator works those out.
Related calculators
- MPG converterConvert UK mpg, US mpg, litres per 100 km and km per litre.
- Electric vs petrol car running costYearly fuel cost of an electric car against petrol or diesel, at your mileage.
- EV charging time calculatorHow long an electric car takes to charge, on a 3-pin plug, wallbox or rapid charger.
- Mileage allowance calculatorHMRC approved mileage rates for 2026 to 2027: what you can be paid tax-free, or claim back.
- Car tax calculatorHow much vehicle tax (VED) a car costs a year, by CO2 and age.
- Stopping distance calculatorHighway Code stopping distances at any speed, in dry, wet or icy conditions.
Save or share this calculator
Embed this calculator
Free to use on your website, blog or newsletter. Copy this code and paste it into your page.