Fuel Cost Calculator UK
Work out the petrol or diesel cost of any UK journey. Enter distance, MPG and price per litre to see fuel used, cost per mile and the total trip cost.
Last updated 21 June 2026 · Written and reviewed by Mustafa Bilgic
Fuel cost calculator
Distance, MPG and price per litre.
Estimate only — figures use the latest published UK rates. Always confirm on GOV.UK.
How much will this journey cost in fuel?
The fuel cost of any trip depends on three things: how far you drive, how economical your car is (its miles per gallon, or MPG), and the price of fuel per litre. Because UK fuel is sold in litres but economy is quoted in miles per gallon, the calculation has to convert between them — there are 4.546 litres in a UK gallon. This tool does that for you and shows the cost per mile too.
A 120-mile trip in a car doing 45 MPG with fuel at £1.40 a litre uses about 12.1 litres and costs roughly £16.95 one way — around 14p a mile.
How the calculation works
First the tool converts your MPG into miles per litre by dividing by 4.546. Then it divides your journey distance by that figure to find the litres of fuel needed, and multiplies by the price per litre. The formula is: cost = (miles ÷ MPG) × 4.546 × price per litre. For a return trip it simply doubles the distance.
Typical MPG and fuel prices
| Car type | Typical MPG |
|---|---|
| Small petrol city car | 50–60 |
| Mid-size petrol | 40–50 |
| Diesel estate / SUV | 45–55 |
| Large petrol SUV | 25–35 |
Use your car's official combined MPG as a starting point — real-world economy is usually a little lower.
Cut your fuel costs
Real-world MPG is often below the official figure, especially in town and at motorway speeds. Smooth driving, correct tyre pressures and removing roof boxes all help. If you are weighing up an electric car, compare the cost with our EV charging cost calculator. For the cost of running a car per mile, see our petrol cost per mile calculator, and budget for road tax too.
Frequently asked questions
How do I calculate fuel cost for a journey?
Divide the distance by your car's MPG, multiply by 4.546 (litres in a UK gallon) to get the litres used, then multiply by the price per litre. For example, 120 miles at 45 MPG and £1.40 a litre costs about £16.95.
How many litres are in a UK gallon?
There are 4.546 litres in a UK (imperial) gallon. This matters because car economy is quoted in miles per gallon but fuel is sold in litres, so the two must be converted to work out the cost.
What is a good MPG?
For a petrol car, 40–50 MPG is typical and over 55 MPG is very economical. Small city cars and efficient diesels can exceed 60 MPG, while large petrol SUVs may only manage 25–35 MPG.
Why is my real MPG lower than the official figure?
Official MPG comes from a standard lab test. Real-world driving — short trips, cold starts, motorway speeds, air conditioning and a heavy load — usually pushes actual economy 10–20% below the quoted figure.
How much does a return trip cost?
A return trip uses twice the fuel of a one-way trip over the same route, so simply double the one-way cost. Select 'Return' in the calculator to do this automatically.