Fuel cost calculator
Trip fuel cost from distance, fuel economy and price, or your car’s gas mileage.
About this calculator
This fuel cost calculator works out how much a road trip will cost in gas, petrol or diesel. Enter the distance, your car's fuel economy and the price of fuel.
It can also work out your gas mileage from the distance driven and the fuel used, in mpg or litres per 100 km.
How it works
Fuel needed is distance ÷ miles per gallon, or distance × litres per 100 km ÷ 100. Multiply by the price for the cost. Fuel economy works the other way: distance ÷ fuel used.
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Worked example
- Work out: Trip fuel cost
- Units: Miles and gallons
- Distance: 300 miles
- Fuel economy: 28 mpg
- Fuel price per gallon: $3.50
- Journey: One way
- Split between: 1 people
Fuel cost: $37.50 (one way)
Common questions
How do I work out my car's mpg?
Fill the tank, reset the trip meter, drive as normal, then fill up again. Divide the miles driven by the gallons you put in.
How do I convert mpg to L/100 km?
Divide 235.2 by the US mpg figure. So 30 mpg is about 7.8 L/100 km. For UK gallons, divide 282.5 by the mpg.
How can I use less fuel on a trip?
Keep your tyres properly inflated, drive at a steady speed, remove roof boxes when you don't need them and avoid carrying extra weight.
Sources and further reading
The story behind it
Where the idea came from: US fuel economy standards and window labels grew out of the oil crisis of the 1970s.
When oil prices jumped in 1973, long queues formed at petrol stations and fuel economy suddenly mattered. The US passed laws in 1975 that set efficiency targets for new cars, and mpg figures became a standard part of buying one. Knowing your car's real fuel use is still the key to budgeting a trip.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, so please double-check anything important.
- Spotted a mistake? Tell us and we'll look into it.
After 15 years as a mathematics educator, I built CalculStore to give students, teachers, professionals and anyone working with numbers simple, reliable tools.
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