Price any journey in petrol or diesel and split the cost between passengers.
Uses the UK gallon of 4.54609 litres. Pump prices change every week, so enter the price you actually pay. Real economy varies with speed, traffic, load and weather.
Planning a road trip, a weekly commute or a lift share? This fuel cost calculator UK works out exactly how much petrol or diesel a journey uses and what it costs at the price you pay. Seeing the cost of each mile, alongside the Energy Saving Trust advice on efficient driving, makes it easier to spot where a few simple habits could save you money on every trip.
Quick answer: A fuel cost calculator UK drivers use applies miles ÷ mpg × 4.54609 × price per litre, converting UK gallons to litres. A 100 mile trip in a car that does 45 mpg uses 10.10 litres, so at 175p a litre it costs £17.68, or about 17.7p a mile.
In This Guide
What Is a Fuel Cost Calculator?
A fuel cost calculator turns three numbers into a journey price: the distance, your car's fuel economy and the pump price. UK cars quote economy in miles per UK gallon, while fuel is sold by the litre, so the calculator converts between the two using the UK gallon of 4.54609 litres.
The formula is miles ÷ mpg × 4.54609 × price per litre. A 100 mile trip in a car that does 45 mpg uses 2.22 gallons, which is 10.10 litres. At 175p a litre that costs £17.68, or about 17.7p a mile.
How Do You Use the Fuel Cost Calculator UK?
Step 1: Enter the Distance
You type the journey distance in miles from your sat nav or a route planner, and choosing Return doubles the distance for you. Type the journey distance in miles from your sat nav or a route planner. Choose Return if you are driving there and back, and the calculator doubles the distance for you.
Step 2: Add Your Fuel Economy
Enter your real world mpg from the trip computer, as this is usually lower than the official figure. If you only know your economy in litres per 100 km, the L/100km to mpg converter gives you the UK mpg figure in seconds, ready to paste here.
Step 3: Choose Fuel and Price
Pick petrol or diesel to load an example price, then overwrite it with the price on your receipt or the forecourt sign. Prices change weekly, so using your own figure keeps the result accurate.
Step 4: Split and Read the Results
Enter how many people are sharing the trip to see each person's share. If the journey is for work, the mileage allowance calculator shows what you can claim at HMRC rates, which you can compare with the real fuel cost shown here.
How Much Does Fuel Cost for a Typical UK Journey?
| Journey | Economy | Price per litre | Fuel cost |
|---|---|---|---|
| 50 miles | 50 mpg | 175p | £7.96 |
| 100 miles | 45 mpg | 175p | £17.68 |
| 200 miles | 40 mpg | 175p | £39.78 |
| 300 miles | 55 mpg | 200p | £49.59 |
At 175p a litre, a 100 mile trip at 45 mpg costs £17.68 in fuel and a 200 mile trip at 40 mpg costs £39.78. Prices in the table are examples only. The government publishes weekly road fuel prices for the UK, which help you sense check a figure before a long trip, although local forecourts can be well above or below the national average.
To improve your mpg, keep tyres at the right pressure and remove roof boxes when not in use. Logging each fill up in our mpg calculator shows whether smoother driving at steady speeds is actually paying off, so you can adjust your habits with real numbers.
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How we checked this tool: the Tools Veria Editorial Team built this tool by hand, checked it against the official rules or published standards where they apply, and tested it against worked examples. Results are estimates for planning, not personal financial or tax advice. Read our editorial policy and disclaimer, or report an error.
Frequently Asked Questions
How do I calculate the fuel cost of a journey?
Divide the miles by your mpg to get gallons, multiply by 4.54609 to get litres, then multiply by the price per litre. For example, 100 miles at 45 mpg and 175p a litre costs £17.68.
How many litres are in a UK gallon?
A UK gallon is 4.54609 litres. A US gallon is smaller, at about 3.785 litres, so US mpg figures are lower for the same car.
How much does petrol cost per mile?
It depends on your economy and the pump price. At 45 mpg and 175p a litre, petrol costs about 17.7p a mile.
Is diesel cheaper to run than petrol?
Diesel usually costs more per litre but diesel cars often return better mpg. Enter both figures in the calculator to compare the cost per mile for your journey.
How do I split fuel costs between passengers?
Enter the number of people sharing the trip and the calculator divides the total fuel cost equally. Some drivers also add a share for wear and parking.
Does the calculator include tolls or parking?
No. It covers fuel only. Add tolls, parking and charges such as congestion zones separately.