Fuel Cost Calculator
Works out the fuel and the money a trip costs from the distance, the fuel efficiency and the price per litre.
Recent
Formula
How the calculation works
Fuel cost is two multiplications deep: the distance divided by the efficiency gives the litres, and the litres times the price give the money. The efficiency is the pivot, because it is what turns a distance into a quantity of fuel.
Because efficiency divides, a smaller number is worse, not better, so a car doing 8 km per litre burns half again as much as one doing 12 over the same trip. That inversion is the most common source of a wrong estimate.
The cost per kilometre is the same figure for every trip in that car, so once you know it, any distance can be priced without redoing the whole sum, and two cars can be compared without fixing a route first.
Common mistakes
- Multiplying by the efficiency instead of dividing. Distance times km per litre gives a meaningless number, not litres.
- Using the price per gallon with litres of fuel. The price and the fuel amount must share a unit, or the total is wrong by the size of a gallon.
- Forgetting the return leg. A one-way figure is half the cost of a there-and-back trip, which is the number most people actually want.
When to use it
- Use it to budget a drive, split fuel between passengers or compare what two cars really cost on the same commute.
- For the total cost of running a car including wear, insurance and servicing, a per-kilometre ownership figure fits better; this tool counts fuel only.
Worked example
320 km at 12 km per litre and 110 per litre costs about 2933.
Common questions
What if I only know miles per gallon?
Convert miles per gallon to km per litre first: 1 mile is about 1.609 km and 1 gallon about 3.785 litres.
What is the cost per km for?
It is a yardstick that ignores trip length, so different routes or different cars can be compared side by side.
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