How to calculate fuel cost for a trip
- Choose petrol/diesel or electric, then enter the trip distance in kilometres or miles. Tick return trip for there and back.
- Enter your car's consumption in the unit you know: L/100 km, km/L, US or UK mpg, or kWh for an EV.
- Enter the fuel or electricity price and, for a shared ride, the number of people splitting the cost.
- Read the total, the cost per person and per km or mile, and share the result with your passengers.
The maths behind it
Fuel used is distance × consumption: a 300 km trip in a car using 7 L/100 km burns 21 litres, which at 1.80 per litre costs 37.80. Miles per gallon works the other way round, as distance per unit of fuel: 250 miles at 30 mpg uses 8.3 US gallons. Note that UK and US gallons differ (4.55 vs 3.79 litres), so a car doing 40 mpg in the UK does about 33 mpg in US terms; choose the right one.
Real consumption depends on speed, traffic, load, air conditioning, tyre pressure and weather. Motorway driving at 130 km/h (80 mph) can use 20–25% more fuel than at 100 km/h (62 mph). Use the figure from your trip computer or a fill-up log rather than the official rating, which is often optimistic. For electric cars, charging losses add roughly 10%, and public rapid chargers usually cost much more per kWh than home charging. Everything is calculated in your browser.
How do I convert mpg to L/100 km?
Divide 235.2 by US mpg (or 282.5 by UK mpg). 30 US mpg is 7.8 L/100 km.
How should passengers split fuel costs?
Commonly equally, including the driver. Some groups also add a small amount for wear and tear or tolls.
Is it cheaper to drive or fly?
For two or more people sharing a car on trips under about 500 km, driving is often cheaper, especially with an efficient car.