Live data, checked today at 15:18 (UK time). 8,155 forecourts: 8,071 from Fuel Finder, the government service every UK forecourt must report its prices to, and 84 from open retailer feeds. Fuel Finder did not answer at our last check, so some prices may be a little older. Wrong price? Report it to Fuel Finder.
MPG calculator: work out your car's miles per gallon
Enter the miles you drove and the litres, or the pounds, it took to fill the tank again. You get your fuel economy in UK mpg, US mpg and litres per 100 km, and what each mile costs at today's UK average of 174.5p a litre, checked 29 September 2026 at 15:18 UK time.
Example figures, 350 miles on 36 litres. Change them above to use your own.
44.2UK mpg, 350 miles on 36 litres
That is 36.8 US mpg or 6.4 litres per 100 km. Each mile costs 17.9p at 174.5p a litre.
Each mile is priced at 174.5p a litre, the average unleaded price across 7,949 stations in the UK, checked 29 September 2026 at 15:18 UK time.
Cost a trip at 44.2 mpg- UK mpg44.2Miles per imperial gallon
- US mpg36.8Miles per US gallon
- Litres per 100 km6.4563.3 km on 36 litres
- Cost per mile17.9p11.2p a km at 174.5p a litre
Pay less for every mile
The cheapest unleaded in the UK today is 153.9p a litre at Gulf, 5-15, High Street, Pondersend. In a car doing 44.2 mpg that is 15.8p a mile against 17.9p at the average price: £21.19 less over 1,000 miles.
See the cheapest petrol in the UK, or search near your postcode:
The same miles in an electric car
| How it is charged | 100 miles | Against your car |
|---|---|---|
| Home, EV off-peak tariff | £2.16 | Saves £15.79 |
| Home, standard rate | £7.11 | Saves £10.84 |
| Public rapid charger | £20.81 | Costs £2.86 more |
Compare with your own electric car, mileage and local prices.
Thinking of charging at home? Search home EV chargers on Amazon UKAs an Amazon Associate, fuelprices.org.uk earns from qualifying purchases. This is an affiliate link, at no extra cost to you. Affiliate disclosure.How this was worked out
- UK mpg: 350 miles ÷ (36 litres ÷ 4.54609 litres per UK gallon) = 44.2 mpg.
- US mpg: 350 miles ÷ (36 litres ÷ 3.785411784 litres per US gallon) = 36.8 mpg.
- Litres per 100 km: 36 litres ÷ 563.3 km × 100 = 6.4 (350 miles × 1.609344 = 563.3 km).
- Cost per mile: 36 litres × 174.5p ÷ 350 miles = 17.9p.
How to work out your mpg from a full tank
- Fill the tank until the pump clicks off, and set the trip meter to zero (or note the odometer).
- Drive as you normally do. The more of the tank you use, the less a single pump click-off matters.
- Fill up again the same way, at the same pump if you can, and note the litres the pump says you added, or the money if that is all you have.
- Enter the trip-meter miles and that fuel in the calculator above. With money, choose "£ spent" and type the price per litre from your receipt for the most accurate answer.
- For a steadier figure, repeat over two or three tanks, then add up all the miles and all the litres before dividing.
By hand: 350 miles on 36 litres is 350 ÷ 36 = 9.72 miles per litre, and one UK gallon is 4.54609 litres, so 9.72 × 4.54609 = 44.2 mpg.
UK mpg, US mpg and litres per 100 km side by side
Find your car's UK mpg in the first column to read the same figure in US gallons and litres per 100 km, and what a mile costs at today's UK average: unleaded 174.5p, diesel 199.7p a litre.
| UK mpg | US mpg | Litres per 100 km | Petrol, per mile | Diesel, per mile |
|---|---|---|---|---|
| 20 mpg | 16.7 | 14.1 | 39.7p | 45.4p |
| 25 mpg | 20.8 | 11.3 | 31.7p | 36.3p |
| 30 mpg | 25 | 9.4 | 26.4p | 30.3p |
| 35 mpg | 29.1 | 8.1 | 22.7p | 25.9p |
| 40 mpg | 33.3 | 7.1 | 19.8p | 22.7p |
| 45 mpg | 37.5 | 6.3 | 17.6p | 20.2p |
| 50 mpg | 41.6 | 5.6 | 15.9p | 18.2p |
| 55 mpg | 45.8 | 5.1 | 14.4p | 16.5p |
| 60 mpg | 50 | 4.7 | 13.2p | 15.1p |
| 65 mpg | 54.1 | 4.3 | 12.2p | 14.0p |
| 70 mpg | 58.3 | 4 | 11.3p | 13.0p |
Questions
How do I calculate mpg from miles and litres?
Divide the miles you drove by the litres you used to get miles per litre, then multiply by 4.54609, the number of litres in a UK gallon. For example 350 miles on 36 litres is 350 ÷ 36 × 4.54609 = 44.2 mpg. The calculator above does this and shows the sum with your own numbers.
How do I work out my mpg if I only know how much I spent?
Turn the money into litres first: divide the pounds spent by the price per litre in pounds. At today's UK average of 174.5p a litre, £60 buys 34.4 litres, and 350 miles on that is 46.3 mpg. Your receipt's price is better than the average, so type it into the price box and choose "£ spent".
What is the difference between UK mpg and US mpg?
The gallon. A UK (imperial) gallon is 4.54609 litres and a US gallon is 3.785411784 litres, so the same car gets a bigger mpg figure in the UK: 40 UK mpg is 33.3 US mpg. Multiply a US mpg figure by 1.20 to get UK mpg. Cars sold in the UK show imperial mpg, so convert any figure from a US website or forum before comparing.
How do I convert mpg to litres per 100 km?
Divide 282.48 by the UK mpg figure. That number is 100 km in miles (62.14) times the litres in a UK gallon (4.54609). For example 45 mpg is 6.3 litres per 100 km, and 6.3 litres per 100 km is 44.8 mpg: the same sum works both ways.
Why is my mpg lower than the manufacturer's figure?
The brochure figure comes from a laboratory test. Typical real-world (not WLTP-sticker) fuel economy for mixed UK driving: WLTP figures usually overstate real-world economy by 15-25%. Our calculators start from 45 mpg for petrol and 55 mpg for diesel as typical real-world figures, and your own tank-to-tank figure is the one that matters for your running costs.
How accurate is a figure from one tank?
It is a good guide, not a measurement: it depends on where the pump clicked off both times, how full each tank was and how you drove. Repeat it over two or three tanks and add all the miles and all the litres before dividing to average the errors out.
How much does each mile cost at my mpg?
At today's UK average of 174.5p a litre, a petrol car doing 35 mpg pays 22.7p a mile, one doing 45 mpg pays 17.6p and one doing 55 mpg pays 14.4p. A diesel car doing 55 mpg pays 16.5p a mile at 199.7p a litre. The calculator above shows the cost per mile for your own figure, and the fuel cost calculator turns it into the cost of a whole trip.
Where does the fuel price in the calculator come from?
It is the average of the current prices at the UK forecourts in our data (7,949 stations report unleaded), taken from the government's Fuel Finder service and retailers' open price feeds, and checked 29 September 2026 at 15:18 UK time. You can pick a nation or a city, or type the price on your own receipt.
More from our fuel price data
Sources and assumptions
- Fuel prices: 7,949 stations report unleaded and 8,060 report diesel in our data, from the government's Fuel Finder service (Open Government Licence v3.0) and retailers' open price feeds, checked 29 September 2026 at 15:18 UK time.
- UK gallon: 4.54609 litres (the imperial gallon). US gallon: 3.785411784 litres (231 cubic inches). Distances use 1.609344 km to the mile.
- Typical fuel economy: Typical real-world (not WLTP-sticker) fuel economy for mixed UK driving: WLTP figures usually overstate real-world economy by 15-25%.
- Electric comparison: the tariffs and efficiency of our EV running-cost calculator, checked 26 September 2026. Home rate: Ofgem energy price cap, Direct Debit GB average, 1 October to 31 December 2026 (ofgem.gov.uk). Public rapid charging: Zapmap EV Charging Price Index, weighted UK average for 50kW+ rapid/ultra-rapid chargers, pay-as-you-go, August 2026 (zapmap.com).
The arithmetic is shown above so you can check it. Fuel used depends on speed, load, weather and how you drive, so treat the result as an estimate. See about our data for how coverage is measured.