How Do I Calculate My Fuel Cost?
Use our fuel cost calculator to work out how much a single journey or your annual mileage will cost in petrol, diesel or electricity.
Whether you are planning a long trip or trying to budget your monthly driving costs, knowing your fuel spend helps you make better decisions. Enter your journey details or annual mileage, and the calculator does the rest.
Fuel is one of the biggest costs of running a car, alongside car insurance, road tax and servicing. Understanding what you spend per mile can also help you choose the right vehicle and the right policy.
A petrol car at 40mpg costs around 17p per mile; an electric car on a home charger costs 2 to 7p. Knowing your real cost per mile matters beyond budgeting, because underestimating mileage to get a cheaper insurance quote can invalidate your policy. Insurers check against MOT records at renewal.
Declare your actual mileage when you compare car insurance quotes.
How do you use the fuel cost calculator?
Select your fuel type, enter your journey or mileage details, and the calculator shows your estimated cost instantly. You can adjust the fuel price and fuel efficiency to match your vehicle.
For a single trip
Choose your fuel type (petrol, diesel or electric), select ‘single trip’, and enter your start and end locations. The calculator uses the distance between them to estimate your fuel cost.
You can change the price per litre to match what you pay locally, or leave the default UK average. Adjust the miles per gallon (mpg) figure to match your vehicle’s real-world consumption.
For annual mileage
Select ‘annual mileage’ and enter the number of miles you drive each year. The average UK driver covers around 7,400 miles annually.
The calculator breaks your annual cost down into weekly and monthly figures. This is useful for budgeting or comparing the running costs of different vehicles before you buy.
How much does fuel cost in the UK?
UK fuel prices change weekly based on wholesale oil costs, exchange rates and government duty. The RAC Fuel Watch tracker provides daily updates on average pump prices across the country.
What are petrol and diesel prices right now?
As of mid-2026, the UK average price for unleaded petrol is around 150p per litre and diesel is around 165p per litre. Prices vary by region and retailer, with motorway services typically charging 10-15p more per litre than supermarkets.
How much does it cost to charge an electric car?
Charging an electric car at home costs around 7-10p per kWh on an overnight EV tariff, or roughly 26p per kWh on a standard rate. Public rapid chargers cost between 54p and 79p per kWh depending on the network and speed.
On average, an electric car costs around 2-7p per mile to run on a home charger. A petrol car doing 40mpg at 150p per litre costs roughly 17p per mile, making EVs substantially cheaper mile for mile.
How do you calculate fuel cost per mile?
Divide the price of one gallon of fuel by your car’s miles per gallon (mpg) figure. One gallon is 4.546 litres, so multiply the price per litre by 4.546 to get the cost per gallon.
What is the formula?
Cost per mile = (price per litre x 4.546) / mpg. For example, at 150p per litre with a car doing 40mpg: (1.50 x 4.546) / 40 = 17.0p per mile.
To calculate a full journey, multiply the cost per mile by the distance. A 200-mile trip at 17p per mile would cost around £34 in fuel.
What about HMRC mileage rates?
If you use your own car for work, HMRC lets you claim 55p per mile for the first 10,000 miles and 25p per mile after that. These are approved mileage rates designed to cover fuel, wear and insurance combined.
Businesses running a fleet can use actual fuel costs instead, but they need to keep detailed records of every fill-up and journey.
Related: What Is Fleet Management?
How can you reduce your fuel costs?
Small changes in driving habits can cut your fuel bill by 10-15% without any mechanical work. The biggest savings come from smoother driving and proper tyre maintenance.
How does driving style affect fuel consumption?
Harsh acceleration and late braking waste fuel on every journey. Driving at a steady speed in the highest appropriate gear keeps revs low and reduces consumption.
This is one reason black box insurance policies can encourage better driving. Smoother driving earns lower premiums and uses less fuel at the same time.
What else makes a difference?
Check your tyre pressures at least once a month. Underinflated tyres increase rolling resistance and can add 3% to your fuel bill.
Remove roof racks and boxes when you are not using them, clear heavy items from the boot, and avoid idling the engine. At motorway speeds, air conditioning uses less fuel than open windows.
| Fuel saving tip | Typical saving |
| Drive smoothly, avoid harsh acceleration | Up to 15% |
| Keep tyres at correct pressure | Up to 3% |
| Remove roof rack when not in use | Up to 10% at motorway speeds |
| Avoid short trips with a cold engine | Up to 5% |
| Use cruise control on motorways | Up to 5% |
| Switch off engine when stationary | Variable (saves idle fuel) |
Does your annual mileage affect car insurance?
Yes, the number of miles you drive each year directly affects your insurance premium. Drivers who cover fewer miles generally pay less because they are statistically less likely to be involved in an accident.
Should you declare your mileage accurately?
Always, because underestimating your mileage to get a cheaper quote can invalidate your policy if you need to make a claim. Most car insurance providers check mileage at renewal using MOT records.
If your mileage drops, for example after switching to working from home, contact your insurer to update the figure. A multi-car policy can also help if you are splitting mileage across two vehicles.
Who pays the most?
High-mileage drivers such as commuters and delivery workers pay more than low-mileage retirees or learner drivers who only drive occasionally. Young drivers also face higher premiums partly because they tend to cover fewer insured miles, pushing up the per-mile risk.
If you only need cover for a short period, temporary car insurance lets you pay by the day or week without committing to an annual policy.
Fuel costs also affect other vehicle types. Van drivers and motorcyclists can use the same calculator by adjusting the mpg and fuel price inputs.
Frequently Asked Questions (FAQs)
Multiply the number of litres by 0.22 to get UK gallons, or divide by 4.546. One UK gallon equals 4.546 litres.
The average petrol car in the UK achieves around 36-40mpg in real-world driving. Diesel cars typically achieve 40-50mpg, while hybrids can exceed 60mpg.
Usually yes, because diesel engines are more fuel efficient. A diesel car doing 50mpg costs around 15.0p per mile at 165p per litre, compared to 17.0p per mile for a petrol car doing 40mpg at 150p per litre.
At 150p per litre and 40mpg, driving 100 miles costs around £17.05 in petrol. In an electric car charged at home, the same distance costs around £5-7.
Prices depend on location, competition, brand and whether the station is on a motorway. Supermarket fuel is typically the cheapest, while motorway services charge a premium.
If you drive your own car for work (not commuting), you can claim HMRC approved mileage rates: 55p per mile for the first 10,000 miles and 25p per mile after that.
Vehicle tax (VED) is based on CO2 emissions for cars registered after April 2017, so less fuel-efficient cars produce more CO2 and pay higher vehicle tax rates. Electric cars currently pay the standard flat rate.