How to use this calculator
- Enter the Trip distance (km) and choose One way or Round trip.
- Enter your car's Fuel use (litres per 100 km) from the manual or trip computer.
- Enter the Fuel price per litre.
- Set People sharing the cost to see each person's share, alongside the total, litres and cost per km.
How fuel cost is calculated
Fuel use is quoted as litres per 100 km, so the fuel for a trip is the distance divided by 100 times that figure. Multiply the litres by the price per litre and you have the cost. A round trip simply doubles the distance.
Cost = (distance · L/100 km ÷ 100) · price per litre- distance = km driven (doubled for a round trip)
- L/100 km = litres burned per 100 km
- price per litre = what you pay at the pump
- Cost per person = cost ÷ people sharing
The calculator also converts your consumption to miles per gallon (US), which is useful if you compare with figures quoted that way.
Because the result scales linearly, you can sanity-check it quickly: 100 km at 7 L/100 km burns 7 litres, so at $1.60 a litre every 100 km costs about $11.20. Use that as a rule of thumb for your own car and price.
Example: a 300 km trip
A car using 7 L/100 km needs 21 litres for 300 km. At $1.60 per litre that is $33.60 one way, or $0.11 per km. Consumption of 7 L/100 km equals about 33.6 mpg (US).
Make it a round trip with three people in the car and the distance is 600 km, fuel needed is 42 litres, the total is $67.20 and each person pays $22.40.
Comparing cars and routes
The same trip with a thirstier car makes the gap clear. At 10 L/100 km instead of 7, the 300 km one-way trip needs 30 litres, which is $48 at $1.60. Over many trips that difference adds up, so use the calculator to compare vehicles before buying with the auto loan calculator.
Real consumption varies with speed, load, traffic and temperature. Your trip computer's average is a better input than the brochure figure.
For longer journeys, compare the fuel cost with the alternatives. A train or coach ticket can be cheaper for one person, while a car often wins when three or four people share it, because the fuel cost per person falls quickly as the number of passengers rises. Remember to count parking and tolls on the car side before deciding.
Ways to spend less on fuel
- Drive at steady speeds; high motorway speeds raise consumption sharply.
- Keep tyres inflated to the recommended pressure and remove unused roof racks.
- Share the ride and split the cost; the people field shows each share.
- Plan the route to avoid heavy traffic and unnecessary detours.
- Compare prices along the route; filling up before a long motorway stretch can be cheaper.
Assumptions and limits
The calculator uses one average fuel-use figure and one price. It does not include tolls, parking, wear, insurance, depreciation or the cost of electricity for electric vehicles. Distances are in kilometres and fuel in litres; for miles and gallons, convert first (1 mile is 1.609 km, 1 US gallon is 3.785 litres).
For the full running cost of a car, add maintenance and ownership costs on top of fuel.
Frequently asked questions
How do I calculate the fuel cost of a trip?
Divide the distance by 100, multiply by your litres per 100 km, then multiply by the price per litre.
How do I convert L/100 km to mpg?
For US gallons, divide 235.215 by the L/100 km figure. For example, 7 L/100 km is about 33.6 mpg.
Should I double the distance for a round trip?
Use the Round trip option; it doubles the distance for you.
How accurate is the estimate?
It is as accurate as your fuel-use input. Speed, load, weather and traffic change real consumption.
How should passengers split fuel costs?
Most people divide the fuel evenly between everyone, including the driver. Tolls and parking can be added to the total and divided the same way.