Fuel Cost Calculator

How does this fuel cost calculator work?

A fuel cost calculator turns three numbers into a trip budget. You need the distance, how much fuel your car uses and the pump price. First it works out the fuel used, then it multiplies that by the price. For example, 280 miles at 45 mpg uses 28.29 litres, so at £1.72 a litre the trip costs £48.65.

I built the tool around three questions.

• Single trip: total cost, fuel used and the cost per mile, km or person.
• Europe route: a drive through several countries, priced leg by leg.
• Europe prices: petrol, diesel and LPG averages for the EU and the UK.

Switch between Metric, UK mpg and US mpg at the top. If you only know a figure in another unit, the unit converter handles miles, kilometres and gallons. Everything runs in your browser, because our server only supplies the official price table.

How do you convert mpg to litres per 100 km?

UK drivers buy fuel by the litre but quote economy in miles per gallon. That mix is where many trip estimates go wrong. The fix is to use the legal definitions. The Weights and Measures Act 1985 sets the UK gallon at 4.54609 litres. A mile is 1,760 yards, or 1.609344 km, and a US gallon is smaller at 3.785411784 litres.

From those constants come three shortcuts.

• UK mpg to L/100 km: divide 282.481 by the figure, so 45 mpg equals 6.28 L/100 km.
• US mpg to L/100 km: divide 235.215 by the figure, so 45 mpg (US) equals 5.23 L/100 km.
• Litres for a trip in UK units: miles × 4.54609 ÷ mpg.

As a result, the same car shows a higher mpg figure in UK units. Mixing them up skews the budget. A UK figure entered as US mpg understates fuel use by about 17%. However, a US figure entered as UK mpg overstates it by about 20%. For quick checks like that, the percentage calculator helps.

Why does real-world fuel economy differ from the official figure?

The official figure comes from a laboratory test. Real driving, however, adds traffic, speed, air conditioning and luggage. The European Commission measured the gap with data from fuel consumption meters in new cars. Its 2024 report found that new petrol cars registered in 2021 used on average 23.7% more fuel than their official value. For diesel cars the gap was 18.1%, and plug-in hybrids emitted 3.5 times their official CO2 value.

So I recommend entering your own economy rather than the brochure number. Two simple methods work.

1. Trip computer: read the average after a long drive, not a short run into town.
2. Brim to brim: fill the tank and reset the trip meter. At the next fill, multiply the miles by 4.54609 and divide by the litres you added.

Motorway speeds and a loaded boot also raise consumption. That is why I add a small margin to holiday budgets.

Where does the fuel cost calculator get European prices?

For EU countries the fuel cost calculator uses the European Commission's Weekly Oil Bulletin. Member states send their data on Wednesday, and the bulletin goes out on Thursday. The table then carries the date of the Monday the prices refer to.

Three points matter when you read it.

• Taxes included: VAT and excise duty are part of the price, so it sits close to the pump price.
• National average: it is not one station's price, so motorway stations can charge more. Malta is the exception, because the state sets its pump prices.
• Coverage: all 27 EU countries. For the UK I use the DESNZ weekly series, published every Tuesday.

To convert pounds, lira or francs, I use the ECB euro reference rates. The central bank updates them around 16:00 CET on working days. It also publishes them for information purposes only. The tool caches this data on our server and shows the bulletin date on every result. If the bulletin runs late, you see a warning instead of silently old prices.

Which country is cheapest for filling up on a European road trip?

Prices change at every border. So the route mode asks for the distance you will drive in each country and prices each leg separately. To split a route, draw it in Google Maps and read off the border crossings.

The spread can be large. In the bulletin of 21 September 2026, petrol cost €2.348 a litre in Germany and €1.849 in Luxembourg. Filling a 50 litre tank in Luxembourg therefore saved about €25 that week. The Full tank saving card works this out for you. The UK average that week, 172.01p a litre, came to about €1.999 at the ECB rate.

Countries outside the bulletin need a price from you.

• Switzerland, Norway and Türkiye: enter CHF, NOK or lira, and the tool converts it.
• Serbia, North Macedonia, Albania and Montenegro: there is no ECB rate, so enter euros.
• Bosnia and Herzegovina: the mark is pegged at 1 € = 1.95583 KM.

Check the bulletin date before you set off, because prices move from week to week.

How do you work out charging costs for an electric car?

For an EV the unit is the kilowatt hour instead of the litre. The calculator takes miles per kWh in UK units and kWh per 100 miles in US units. In metric it uses kWh per 100 km. For example, 200 miles at 3.5 mi/kWh needs 57.14 kWh. The charging loss box then adds 10% for energy lost between socket and battery, giving 62.86 kWh.

Where the price comes from matters more than the formula.

• Country average: pick a country and the tool uses Eurostat's household electricity price. Eurostat updates it every six months but has no current UK figure, so UK drivers should enter their own tariff.
• Rapid chargers: public rapid charging usually costs more than a home tariff, so type your network's price.

HMRC reflects the same gap in its advisory electricity rate for company cars. From 1 September 2026 it is 7p a mile for home charging and 15p for public charging.

What mileage rates can UK businesses use?

If you drive for work, HMRC publishes two sets of rates. Both sit alongside a real fuel cost calculation.

• Advisory fuel rates: these apply to company cars. From 1 September 2026, petrol is 14p, 17p or 27p a mile by engine size. Diesel is 15p, 16p or 22p, and HMRC reviews the rates every quarter.
• Approved mileage allowance payments: these apply to your own car on business. From 6 April 2026 the rate is 55p a mile for the first 10,000 miles, then 25p.

In practice I compare the advisory rate with the cost per mile this calculator gives for the actual car. If your real cost is higher than the rate, the difference comes out of your pocket. So it is worth knowing before you agree a reimbursement policy.

Check the current HMRC advisory fuel rates before you rely on them, because they change every quarter.

How should transport businesses build fuel into their prices?

For any business that sells time on the road, cost per mile is the floor of the price. If you run transfers, removals or tours, start every quote with fuel. Then add the driver, maintenance, tyres, tolls and insurance. A quote that ignores fuel quietly loses its margin when pump prices rise.

In my experience, firms that tie their price list to cost per mile can update it within minutes. If you also need to show VAT on a quote, the VAT calculator gives net and gross side by side.

Knowing your costs is half the job; the other half is being found. People who need an airport transfer or a removal firm search on Google. In Google Ads management I focus these accounts on searches that ask for a quote. I explain how I set the spend in how to set a Google Ads budget. The logic matches this page: unit cost first, then the target.