Fuel Cost Calculator
Work out the petrol or diesel cost of any UK journey from your distance, MPG and pence-per-litre — with the return-trip total and the cost per mile.
Fuel cost calculator
Petrol & diesel. UK gallon = 4.546 litres.
Real-world MPG varies with driving, load and traffic. Compare fuel prices before a long trip.
How fuel cost is worked out
To find the cost of a journey you need three things: how far you are going (miles), how efficient your car is (MPG) and the price per litre. The calculation converts MPG into litres used — using the UK imperial gallon of 4.546 litres — then multiplies by the pump price.
Cost = (miles ÷ MPG × 4.546) × price-per-litre. A 100-mile trip at 45 MPG and 140p/litre uses about 10.1 litres and costs roughly £14.14 one way, or £28.28 there and back.
Typical UK fuel economy
| Car type | Typical real-world MPG |
|---|---|
| Small petrol city car | 50–60 MPG |
| Family petrol hatchback | 40–50 MPG |
| Diesel saloon / estate | 50–65 MPG |
| Large SUV / 4×4 | 25–35 MPG |
Real MPG is usually below the official figure, especially in town. Cost per mile uses your own MPG and price.
Cutting your fuel bill
Small changes add up over a year: keeping tyres correctly inflated, removing roof boxes when not in use, easing off harsh acceleration, and comparing prices — supermarket forecourts are often a few pence cheaper. Knowing your cost per mile also helps with mileage claims and deciding whether a journey is worth driving. To budget your monthly motoring costs, pair this with our budget calculator.
Frequently asked questions
How do I calculate fuel cost for a journey?
Work out how many litres the trip uses (distance in miles ÷ MPG × 4.546), then multiply by the price per litre. The calculator does this and shows the total, the return-trip cost and the cost per mile.
How many litres are in a UK gallon?
A UK imperial gallon is 4.546 litres. MPG (miles per gallon) in the UK uses the imperial gallon, so the calculator converts your MPG to a cost using 4.546 litres per gallon.
What is a typical MPG for a UK car?
Many modern petrol cars average 40 to 55 MPG, diesels often 50 to 65 MPG, and small efficient cars can exceed 60 MPG. Real-world MPG is usually lower than the official figure, especially in town.
How do I work out cost per mile?
Cost per mile is the total fuel cost divided by the miles driven. The calculator shows this automatically, which is handy for claiming mileage or comparing journeys.
Does this include electric vehicles?
This tool is for petrol and diesel cars priced per litre. For an electric car you would instead use pence per kWh and miles per kWh, which work differently.