Work out what a trip will cost in fuel or electricity, and how much each passenger should chip in.
Loading the tool…
Fuel economy conversions
| UK MPG | US MPG | Litres per 100 km |
|---|---|---|
| 30 | 25 | 9.4 |
| 40 | 33 | 7.1 |
| 50 | 42 | 5.6 |
| 60 | 50 | 4.7 |
A UK (imperial) gallon is 4.546 litres and a US gallon is 3.785 litres, so the same car shows a higher MPG figure in the UK. To convert UK MPG to L/100 km, divide 282.5 by the MPG.
Getting an accurate figure
- Use your car’s real-world MPG from the trip computer, not the brochure figure.
- Check today’s pump price: prices change weekly and vary between supermarkets and motorway services.
- For electric cars, home charging costs far less per kWh than public rapid chargers, so pick the price for where you’ll charge.
For business mileage in the UK, HMRC’s approved rate for 2026/27 is 55p a mile for the first 10,000 miles, which also covers wear and tear, insurance and servicing, not just fuel.
Frequently asked questions
How do I work out fuel cost per mile?
Price per litre × 4.546 ÷ UK MPG. At 140p a litre and 45 MPG that’s about 14p a mile.
What's a good MPG?
Small petrol cars often get 45 to 55 MPG on a run, and larger SUVs 30 to 40.
How do I split fuel costs with passengers?
Enter the number of people sharing, and the tool divides the cost.
Does it work for electric cars?
Yes, choose miles per kWh or kWh per 100 km and a price per kWh.
Sources
Last updated: