Fuel Cost Calculator

Three numbers do almost all the work: the distance you are driving, your car's MPG (or litres per 100km, or miles per kWh for an EV), and the price you are paying per litre or per kWh. Drop those in and you get total fuel needed plus the cost. With petrol around £1.45 per litre in April 2026 and a typical family car returning 45 mpg, a 200-mile round trip works out at roughly £29 in fuel; the same trip in a 24 mpg SUV is closer to £55.

The calculator handles both miles and kilometres, both MPG and L/100km, and lets you set up several vehicles side by side so you can see the cost gap before deciding which one to take. The bottom line is simple: you want a low cost per mile, and that depends much more on the car you choose than on whether the trip is long or short.

On a 300-mile run, the differences are clear. A 50 mpg diesel needs about 27 litres of fuel; at £1.50 per litre that is roughly £40. A 35 mpg petrol uses 39 litres at £1.45, which is around £57. A typical EV doing 3.5 miles per kWh uses 86 kWh; at home overnight rates of around 7.5p per kWh that is just £6.50, but at public rapid rates of 80p per kWh it is £69, more than the petrol car.

The headline lesson is that EV running costs swing wildly based on where you charge. With a home wallbox on an off-peak tariff, an EV is around six times cheaper to fuel per mile than petrol. Without home charging, the picture flattens; using only public rapid chargers, an EV can actually cost more per mile than a frugal diesel on the same trip.

The pump price you see is one of the more variable numbers in personal finance. Motorway services routinely add 15p to 25p per litre over supermarket forecourts, so on a 60-litre tank fill you can pay £15 more for the convenience. Plan a long trip around a single supermarket fill where possible, and your trip cost drops accordingly.

Real-world MPG is also typically 10 to 20% lower than the official figure. The brochure number is run on a lab cycle that is gentler than real driving. To get a personal MPG figure, reset the trip computer on a 100-mile motorway run and read the average. Or fill the tank, drive a tank, refill, and divide litres used by miles. That figure, fed into the calculator, gives you a cost estimate that will match what your bank statement actually shows.