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How trip cost is calculated
The fuel cost of a trip is simply the distance driven multiplied by the fuel your car uses per unit distance, times the price of fuel. In US units: cost = miles ÷ MPG × $/gal. In metric: cost = km × (L/100km ÷ 100) × $/L. The calculator uses a common internal base so switching units never changes the answer.
If you are travelling with others, the calculator divides the total cost by the number of people to show the fair share for each passenger. This is a quick and transparent way to split fuel on a shared trip — though you may also want to account for tolls, parking and wear-and-tear if you want a fully accurate split.
The "round trip" option is there so you can record whether the distance you entered is a one-way journey or a full out-and-back trip. Whichever you choose, enter the total distance you will actually drive, because the fuel cost depends only on how far the wheels turn — a 200 km round trip and a 200 km one-way trip use exactly the same amount of fuel.
The result is an estimate. Real-world fuel consumption changes with speed, terrain, load and weather, so treat the number as a guide rather than an exact figure. For longer road trips, it is also worth budgeting separately for tolls, parking and any accommodation along the way.
If you are not sure of the distance, you can measure it with a mapping app or take the reading from your car's trip odometer before and after the journey — then drop the number straight into the field above.
Related tools
- Commute cost calculator — for a regular, repeating journey.
- Car comparison calculator — compare two cars' yearly fuel cost.
- EV charging calculator — see how an electric car compares.