Energy and vehicle · Fuel
Calculate the fuel cost of a trip
Three numbers are enough: distance, economy per 100 km and price per litre. The tool returns litres, total cost and cost per kilometre.
Calculate
How the calculator works
The arithmetic is direct. Litres are distance × economy ÷ 100, because economy is quoted per 100 kilometres. The cost is those litres multiplied by the price per litre. Cost per kilometre divides the total by the distance: that is the figure to compare between two vehicles, or between driving and the train.
Formula and method
litres = distance × economy ÷ 100
Economy is given per 100 km, hence the division.
cost = litres × price per litre
Pump price, taxes included.
cost/km = cost ÷ distance
Lets you compare two vehicles or two modes of transport.
The tool does not model your driving or the traffic: it applies the economy figure you enter. An average taken over several tanks is far more reliable than the type-approval number, which comes from a standardised cycle. Tolls, servicing, insurance and depreciation are excluded: this is not a full cost of ownership.
Worked example
500 km at 6.5 L/100 km, fuel at 1.85 per litre
distance = 500, economy = 6.5, price = 1.85.
- Litres: 500 × 6.5 ÷ 100 = 32.5 L.
- Cost: 32.5 × 1.85 = 60.13.
- Cost per km: 60.13 ÷ 500 ≈ 0.12.
32.5 litres, about 60 in fuel, and 12 cents a kilometre.
A return trip of 2 × 220 km
distance = 440, economy = 7.2, price = 1.90.
- Litres: 440 × 7.2 ÷ 100 = 31.68 L.
- Cost: 31.68 × 1.90 = 60.19.
About 60 for the whole round trip.
Input notes
- Distance
- The total distance covered. A return trip counts twice.
- Fuel economy
- Litres burnt per 100 kilometres. Measure it over several tanks.
- Fuel price
- The pump price. A price of zero is accepted, for a company car for instance.
Assumptions and limits
Assumptions
- Economy stays constant over the whole trip.
- The price per litre does not change en route.
- Only fuel is counted, no other running cost.
Limits
- No tolls, servicing, insurance or depreciation.
- No correction for gradient, load, air conditioning or tyres.
- A short urban trip burns more than the average entered, because the engine starts cold.
How to read the result
Cost per kilometre is the most useful number: it compares directly with a train ticket or an employer's mileage rate. Note that such a rate covers far more than fuel, so it is normally higher. If your real economy is one litre worse than the figure entered, the budget rises by roughly 15%: redo the calculation with your true average.
Common mistakes
Entering the manufacturer's type-approval figure.
It comes from a standardised cycle. Measure your own average at the pump.
Forgetting the return leg.
The distance asked for is the total covered, both ways included.
Taking this as the real cost of the vehicle.
It covers fuel only, not servicing or depreciation.
Comparison
| Economy | Litres | Cost | Cost/km |
|---|---|---|---|
| 5 L/100 km | 25 | 46.25 | 0.09 |
| 6.5 L/100 km | 32.5 | 60.13 | 0.12 |
| 8 L/100 km | 40 | 74.00 | 0.15 |
| 10 L/100 km | 50 | 92.50 | 0.19 |
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Frequently asked questions
What does a 500 km trip cost?
About 60 at 6.5 L/100 km.
At 6.5 L/100 km and 1.85 per litre you need 32.5 litres, so roughly 60. The figure moves sharply with economy: at 10 L/100 km the same trip costs nearly 92.
How do I find my real fuel economy?
Fill the tank twice.
Fill up, note the odometer, drive normally, then fill up again. Divide the litres added by the kilometres covered and multiply by 100. That is your real-world economy.
Does this include tolls?
No, fuel only.
Only fuel is counted. Add tolls, parking and servicing separately if you want a complete travel budget.
Author and update
Written by Rédaction HexaCalc (editorial team). Content last updated: August 25, 2026. No third-party medical or financial review is claimed.
- NIST Guide to the SI, Appendix B: Conversion Factors — National Institute of Standards and Technology
Is your economy quoted in mpg?
The converter moves between US or UK mpg and litres per 100 km.
Fuel economy converterCategory: Energy and vehicle