How the cost is calculated
With miles per gallon, fuel used = miles ÷ mpg × 4.54609, because a UK gallon is 4.54609 litres. With litres per 100 km, the calculator converts miles to kilometres (1 mile = 1.609344 km) and multiplies by your L/100 km figure ÷ 100.
The cost is the litres used multiplied by the price per litre in pence, divided by 100 to give pounds. Cost per mile is the total cost divided by the miles driven.
Worked examples
A 100-mile journey in a car that does 45 mpg uses 100 ÷ 45 × 4.54609 = 10.1 litres. At an example price of 140p a litre, that costs £14.14, or £0.14 a mile. The return journey costs £28.29.
The same 100 miles in a car that uses 6.3 litres per 100 km is 160.9 km, which uses 10.1 litres and costs £14.19 at 140p a litre.
Getting a realistic figure
The 140p price is only an example. Fuel prices change often and vary between petrol stations, so enter the price you actually pay.
Official mpg figures are measured in test conditions, and real-world economy is often lower, especially in town traffic, at motorway speeds, in cold weather or with a heavy load. Your car's trip computer or your own fill-ups will give a better figure.
The cost covers fuel only, not wear and tear, parking or tolls.
Inputs for the fuel cost calculator
Distance
The one-way length of your journey in miles.
Fuel economy unit
Choose UK miles per gallon or litres per 100 km, whichever your car's handbook or trip computer uses.
Fuel economy
Your car's fuel economy in UK miles per gallon. A higher figure means less fuel is used. Only shown if you choose miles per gallon.
Fuel economy
Your car's fuel use in litres per 100 km. A lower figure means less fuel is used. Only shown if you choose litres per 100 km.
Fuel price
The price per litre in pence. The figure shown is only an example, so enter the price at your pump.
Return journey?
Choose yes to double the distance for there and back.
CALCULATOR QUESTIONS
Fuel cost calculator questions
How do I work out the fuel cost of a journey?
Divide the miles by your mpg, multiply by 4.54609 to get litres, then multiply by the price per litre. 100 miles at 45 mpg and 140p a litre costs £14.14.
Are UK and US miles per gallon the same?
No. A UK gallon is 4.54609 litres and a US gallon is about 3.785 litres, so the same car shows a higher mpg figure in UK gallons. Use UK mpg figures in this calculator.
How do I convert L/100 km to mpg?
Divide 282.48 by the L/100 km figure to get UK mpg. For example, 6.3 L/100 km is about 44.8 mpg.
How do I split fuel costs for a shared journey?
Work out the total cost, choosing a return journey if needed, and divide it by the number of people sharing.