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Fuel cost calculator

How much will the drive cost? Enter the distance, your car’s fuel consumption and the fuel price – in miles or kilometres.

Units
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Fuel cost
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Fuel needed
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How to use the fuel cost calculator

  1. Choose your units: km and litres per 100 km, miles and US mpg, or miles and UK mpg (UK fuel is sold per litre).
  2. Enter the distance, your car’s fuel consumption and the fuel price.
  3. Tick return trip to double the distance, and split the cost between passengers with the slider.

The formulas

Metric: Cost = km × l/100 km ÷ 100 × price per litre

US: Cost = miles ÷ mpg × price per gallon

UK: Cost = miles ÷ mpg × 4.546 × price per litre

A UK (imperial) gallon is 4.546 litres, while a US gallon is 3.785 litres – so 40 mpg in the UK is not the same as 40 mpg in the US.

Worked examples

USA: 300 miles at 28 mpg

300 ÷ 28 = 10.71 gallons. At $3.40 a gallon the trip costs $36.43.

UK: 200 miles at 45 mpg

200 ÷ 45 × 4.546 = 20.20 litres. At £1.45 a litre that is £29.30.

Europe: 450 km at 6.5 l/100 km

450 × 6.5 ÷ 100 = 29.25 litres. At €1.75 a litre the fuel costs €51.19.

Converting mpg and l/100 km

l/100 km = 235.21 ÷ US mpg = 282.48 ÷ UK mpg

So 28 US mpg is about 8.4 l/100 km, and 45 UK mpg is about 6.3 l/100 km. Note that the scales run in opposite directions: a higher mpg is better, but a lower l/100 km is better.

Real consumption depends on speed, traffic, load, tyre pressure and air conditioning. Motorway driving at high speed can use 20–30% more fuel than the official figure.

Frequently asked questions

How do I find my car’s fuel consumption?
Fill the tank, reset the trip counter, drive normally and fill up again. Divide the miles driven by the gallons added for mpg, or divide the litres added by the kilometres driven and multiply by 100 for l/100 km.
How much fuel does a 100-mile trip use?
At 30 US mpg, 100 miles uses 3.33 US gallons. At 45 UK mpg it uses 2.22 UK gallons, which is about 10.1 litres.
How should we share fuel costs on a road trip?
The simplest fair method is to divide the total fuel cost by the number of people. Use the slider in the calculator to see the share per person.

Last reviewed: November 13, 2026

Results are estimates for general information only and are not financial, tax, medical or legal advice. Check important figures with a qualified professional.