Fuel Cost Calculator
Work out what a journey really costs in fuel using your car’s MPG and the price at the pump, per trip, per week, per month and per year.
miles
miles per gallon (MPG)
pence per litre
Cost per journey
£8.79
£0.15 per mile
- Weekly cost
- £87.89
- Monthly cost
- £380.86
- Annual cost
- £4,570.34
How is fuel cost calculated?
Fuel cost depends on three things: how far you travel, how efficient your car is (its miles per gallon), and the price of fuel. Because UK fuel is sold in litres but efficiency is quoted in miles per gallon, the calculator converts between the two for you using 4.546 litres per UK gallon.
Enter your journey distance, your car’s MPG and the current pump price in pence per litre. Tick the return journey option to double the distance for a round trip.
Getting an accurate figure
Real-world MPG is often lower than the official figure, especially in town or in cold weather. For a realistic estimate, use the average MPG shown on your car’s trip computer rather than the manufacturer’s headline number.
Fuel prices change frequently, so update the pump price for the most accurate result. Comparing petrol and diesel prices, or a more efficient car, quickly shows the potential savings.
Worked example
A 30-mile commute in a car doing 45 MPG, with petrol at 145p per litre, uses about 3 litres each way. That is roughly £4.35 per one-way trip, or £8.70 for a return journey.
Commuting five days a week, that is about £43.50 a week, £188 a month and around £2,262 a year in fuel alone.
Frequently asked questions
Do I enter miles or kilometres?
Enter the distance in miles, because UK fuel economy is measured in miles per gallon. If you only know kilometres, divide by 1.609 to convert to miles first.
Where do I find my car’s MPG?
Most cars show average MPG on the dashboard trip computer. You can also check the official figures for your model, though real-world economy is usually a little lower.
Is the price in pence or pounds?
Enter the pump price in pence per litre, for example 145 for £1.45. The calculator converts it to pounds automatically.
Does this work for electric cars?
This tool is designed for petrol and diesel. Electric running costs are based on pence per kWh and efficiency in miles per kWh, which work differently.
Why is my real cost higher?
Short trips, heavy traffic, cold starts and a loaded car all reduce MPG, which raises the real cost compared with the official economy figure.
Figures last reviewed on 13 August 2025.
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