1. Convert miles and MPG to litres
Litres used = journey miles ÷ UK MPG × 4.54609. A UK gallon contains 4.54609 litres, which is different from a US gallon.
Journey fuel cost calculator UK
Enter a UK start and destination, or use a road distance you already know. Add your fuel economy and pump price to calculate litres used, one-way and return cost, cost per mile and cost per passenger.
How this fuel cost calculator works
Quick maths on the website. Smarter stop decisions in the app.
Enter your start and destination, fuel type, MPG and expected station price. The website calculates litres used, one-way cost, return cost and cost per person from the route and inputs shown. For current station comparisons, extra-driving checks, a wider search radius, saved vehicles and alerts, install Route & Fuel.
Fuel cost formula
How to calculate fuel cost for a journey
The calculator uses UK imperial gallons and a road-distance estimate, so the result is more useful than multiplying a straight-line distance by a rough cost per mile.
2. Apply the fuel price
Journey cost = litres used × price per litre. If the pump price is entered in pence, divide it by 100 before multiplying.
3. Add the journey options
Select a return journey to double the one-way distance, or split the result between passengers. The cheaper-station option also subtracts the fuel used over a detour.
Worked example: 100 miles at 45 UK MPG
A 100-mile journey at 45 UK MPG uses about 10.10 litres. At 150p per litre, the estimated one-way fuel cost is £15.15. Real consumption can differ with traffic, weather, load and driving style, so treat the result as an estimate.
Common questions
Fuel cost calculator questions
How do I calculate fuel cost for a journey?
Divide journey miles by UK MPG, multiply by 4.54609 to get litres used, then multiply litres by the fuel price per litre. This calculator performs those steps using an estimated road route or a distance you enter.
Why does the calculator ask for UK MPG?
A UK imperial gallon is 4.54609 litres, so UK MPG and US MPG produce different answers. Use the UK MPG figure for your vehicle, or switch the calculator to litres per 100km.
Can I calculate a return journey or cost per person?
Yes. Select Return journey to double the one-way route and Split the cost to show an estimated cost per passenger.
Does cheaper petrol still save money after a detour?
Not always. Compare the pump-price saving with fuel used over the extra miles. The optional cheaper-station comparison estimates the saving left after the detour.
Take the calculation into the app
Check real fuel stops before you commit.
The website gives you the quick calculation. Route & Fuel in the app searches a wider radius and checks real stations against your route, live traffic, saved vehicle, fuel type and fuel remaining, then lets you save the journey and fill-up so you can follow costs and savings over time.
