Fuel Cost Calculator UK
Fuel Cost Calculator UK
Estimate petrol or diesel spend for a full year or one journey using your mileage, real-world UK MPG and local pump price.
How fuel cost is calculated
Calculation logic
How fuel cost is calculated
Distance ÷ UK MPG
Dividing miles by real-world UK imperial MPG gives the estimated number of imperial gallons used.
Gallons × 4.54609
Each UK imperial gallon is converted using exactly 4.54609 litres per gallon.
Litres × local price
The entered pence-per-litre price is divided by 100 and multiplied by estimated litres used.
Complete fuel-cost formula
Fuel cost (£) = (distance in miles ÷ real-world UK MPG) × 4.54609 × (fuel price in pence per litre ÷ 100)
Worked example
100 miles at 40 UK MPG and 150p/L costs £17.05. This is an illustration only—enter your own local price.
Use real-world MPG where possible. Official test figures are useful for comparison, but VCA guidance explains that actual consumption varies with factors including driving style, weather and vehicle load.
Fuel calculator guidance
Common fuel-cost questions
How do I calculate fuel cost for a journey?
Divide the total journey distance by the vehicle's real-world UK MPG to estimate imperial gallons used. Multiply by 4.54609 to convert gallons to litres, then multiply by the fuel price in pounds per litre.
Does this calculator use UK or US MPG?
It uses UK imperial miles per gallon. A US MPG figure uses a smaller US gallon and will produce the wrong result in this UK calculator.
What fuel price should I enter?
Enter the price displayed at your chosen filling station in pence per litre. For example, a displayed price of 143.9p should be entered as 143.9. Prices vary by location and forecourt, so no national price is inserted automatically.
Why might my actual fuel cost be different?
Real fuel use can change with driving style, traffic, route, weather, vehicle load, tyre condition and accessories. Use an MPG figure that reflects your own driving where possible.
Does this include electric charging or other ownership costs?
No. This calculator estimates petrol or diesel fuel spend only. It does not include electricity, insurance, road tax, MOT, maintenance, tyres, finance, parking, clean-air charges or depreciation.
Official reference note: the calculator uses the UK imperial-gallon definition for conversion. Fuel price is always supplied by the customer because pump prices differ by location and forecourt.
Last reviewed: 2 September 2026