Fuel Cost Comparison at Your Mileage
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Enter your vehicle details to calculate fuel costs.
How to Calculate Your Fuel Costs
To work out your fuel cost per mile, multiply the price per litre by 4.546 to get the price per gallon, then divide by your car's MPG.
The 4.546 figure matters: UK MPG figures use imperial gallons, not US gallons, which is why American fuel calculators give the wrong answer for a UK car.
Cost per mile = (price per litre × 4.546) ÷ MPG
Example: at £1.35 a litre in a 45 MPG car, that is (1.35 × 4.546) ÷ 45 = 13.6p per mile.
Typical real-world MPG by car type
Manufacturer WLTP figures are usually optimistic. These are realistic everyday numbers to sense-check your own.
| Car type |
Real-world MPG |
Cost per mile at £1.35/litre |
| Small petrol hatchback | 45 to 55 | 11p to 14p |
| Family petrol saloon or estate | 35 to 45 | 14p to 18p |
| Family diesel | 45 to 60 | 11p to 15p |
| Petrol hybrid | 55 to 70 | 9p to 11p |
| Large SUV or 4x4 | 25 to 35 | 18p to 25p |
Five things that genuinely cut fuel costs
- Check tyre pressure monthly. Under-inflated tyres can cost you 3% or more in fuel, and it is free to fix.
- Ease off the motorway speed. Dropping from 80 to 70 mph typically saves around 10% to 15%, because drag rises with the square of speed.
- Take the roof box off when not in use. An empty roof box can cost 10% or more on a motorway run.
- Lose the dead weight. Every 50 kg of clutter costs roughly 1% to 2% in fuel.
- Fill up away from the motorway. Motorway services routinely charge 15p to 25p a litre more than a supermarket forecourt.
Claiming business mileage? If you drive your own car for work, HMRC lets your employer pay
45p per mile tax-free for the first 10,000 business miles in a tax year, then 25p per mile after that. If your employer pays less,
you can claim tax relief on the shortfall. Work it out with the
mileage allowance calculator.
Fuel Cost FAQs
How do I calculate fuel cost per mile in the UK?
Multiply the price per litre by 4.546 to convert it to the price per imperial gallon, then divide by your car's MPG. At £1.35 a litre in a 45 MPG car, that is (1.35 × 4.546) ÷ 45 = 13.6p per mile. Multiply by your journey distance for the trip cost.
How much does it cost to drive 100 miles in the UK?
At £1.35 a litre, roughly £11 to £14 in an economical small car at 45 to 55 MPG, £14 to £18 in a typical family petrol car at 35 to 45 MPG, and £18 to £25 in a large SUV at 25 to 35 MPG. An electric car charged at home is usually £4 to £7 for the same 100 miles.
Why is UK MPG different from US MPG?
The UK uses the imperial gallon of 4.546 litres, while the US gallon is 3.785 litres. A UK gallon is about 20% larger, so the same car shows a higher MPG figure in the UK than in the US. Always use a UK-based calculator for a UK car, or your cost per mile will be understated.
Is diesel still cheaper to run than petrol?
On fuel alone diesel usually wins, because diesel engines return 15% to 25% more MPG, though diesel typically costs more per litre. The gap narrows once you include higher servicing costs, potential DPF problems on short journeys, and clean air zone charges for older diesels. Diesel makes most sense for high annual mileage that is mainly motorway.
Does driving slower actually save fuel?
Yes, within limits. Most cars are at their most efficient between roughly 45 and 60 mph. Above that, aerodynamic drag rises sharply, so going from 80 to 70 mph typically saves 10% to 15%. Below about 40 mph in a high gear, efficiency also falls, so extremely slow driving does not help.
For informational purposes only · Fuel prices change frequently · Check current prices at petrolprices.com