Fuel Cost Calculator
Enter the distance, how many miles per gallon (or litres per 100 km) your car does and the fuel price. We give you the cost of the trip.
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The formula
US: fuel = distance / mpg. Metric: fuel = distance / 100 x L per 100 km. Cost = fuel x price per unit.
Working out a trip
Divide the distance by your fuel economy to get the fuel used, then multiply by the price. A 300 mile trip in a car doing 30 mpg uses 10 gallons, and at 3.50 a gallon that is 35. A round trip doubles it.
Finding your own fuel economy
Fill the tank, reset the trip meter, drive normally, then fill up again. Divide the miles driven by the gallons you added. That real-world figure is better than the one in the brochure.
Things that raise the cost
- Speed: fuel use climbs sharply above about 55 mph (90 km/h).
- Heavy loads, roof boxes and open windows at speed.
- Cold weather and short stop-start trips.
- Under-inflated tyres.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| Miles, US gallons, mpg; Trip distance (miles): 300; Fuel economy (mpg): 30; Fuel price ($ per gallon): 3.5 | Trip fuel cost: $35.00 |
| Miles, US gallons, mpg; Trip distance (miles): 120; Fuel economy (mpg): 25; Fuel price ($ per gallon): 3.8; Round trip | Trip fuel cost: $36.48 |
| Kilometres, litres, L/100 km; Trip distance (km): 450; Fuel use (L per 100 km): 7.5; Fuel price (per litre): 1.75 | Trip fuel cost: $59.06 |
Fuel Cost Calculator: frequently asked questions
How do I use litres and kilometres?
Switch the units to "Kilometres, litres" and enter the fuel use as litres per 100 km.
Does it include tolls or parking?
No, fuel only.
How accurate is this estimate?
It is as accurate as the numbers you give it. Real-world amounts such as paint, concrete or fuel vary, so allow a margin.
Is what I enter in this tool saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Is this tool free to use?
Yes. It is free, needs no sign-up and has no usage limit.
Last reviewed: October 3, 2026