Fuel Cost Calculator
What a trip will cost in fuel, and how much each person pays.
Good to know. Split the fuel, not the friendship: there’s a field for how many are in the car.
How it works
In plain words
Work out how much fuel the trip uses from the distance and your car’s fuel economy, then multiply by the fuel price. Split between passengers if you’re sharing.
The formula
fuel (L) = distance (km) × L/100 km ÷ 100 cost = fuel × price per litre mpg (US) → L/100 km: 235.215 ÷ mpg
Worked example
250 km in a car that uses 6.5 L/100 km needs 16.25 litres. At 1.80 a litre, the trip costs 29.25.
Sources
- NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B Exact conversion factors for US customary units.
- Weights and Measures Act 1985, Schedule 1 1 UK gallon = 4.54609 litres.
Sources checked September 29, 2026. 7 automated tests check its answers on every change.
About the fuel cost calculator
Knowing what a journey costs in fuel is useful for budgeting a road trip, splitting costs fairly with passengers, comparing driving against the train, or claiming mileage.
The calculator accepts fuel economy in the four common formats. Most of Europe uses litres per 100 km, where lower is better. The US and UK use miles per gallon, where higher is better, but the gallons are different sizes: a UK (imperial) gallon is about 4.55 litres and a US gallon about 3.79 litres, so the same car has a higher mpg figure in the UK. Some countries use kilometres per litre. Pick whichever matches your car’s figures.
Official economy figures are measured in test conditions and are often optimistic. Your real consumption depends on speed, traffic, load, weather, air conditioning and driving style. For a better estimate, use your car’s trip computer, or fill the tank, drive, and divide the fuel used by the distance.
Fuel is only part of the cost of driving. Tolls, parking, wear and tear, insurance and depreciation add up too. To compare with an electric car, use the electric vs gas car calculator.
Questions people ask
How do I calculate the fuel cost of a trip?
Multiply the distance by your fuel use per km, then by the price of fuel. 250 km at 6.5 L/100 km uses 16.25 L, which costs 29.25 at 1.80 a litre.
How do I convert mpg to L/100 km?
For US mpg, divide 235.215 by the mpg. For UK mpg, divide 282.481 by the mpg. 30 US mpg is about 7.84 L/100 km.
Why is UK mpg higher than US mpg for the same car?
Because a UK gallon (4.546 L) is about 20% larger than a US gallon (3.785 L).