Advanced options
Depreciation guide: a newish car loses GBP 1,500-3,000/year, an older one GBP 300-800. The 45p/mile HMRC mileage rate is a fair proxy for full costs on an average car, which is why "it only costs me the petrol" undercounts by roughly half. Low-mileage drivers pay the most per mile: the fixed costs spread over fewer miles.
What The Car Cost Per Mile Calculator Works Out
- Cost per mile: the year's fuel (miles divided by mpg, times 4.546 litres a gallon, times the pump price) plus insurance, servicing, MOT, road tax and depreciation, all divided by the miles. The instinctive cost of a journey is the fuel at 12p to 15p a mile, but the honest figure for an ordinary car over an 8,000-mile year is nearer 50p once the fixed stack is spread across the miles.
- Per year: the full annual bill. Depreciation is the invisible heavyweight: a near-new car sheds thousands a year against the elderly hatchback's few hundred, which is why running an older car is the great unsung economy.
- A 100-mile trip really costs: the all-in cost per mile multiplied by the trip, which recalibrates both the "free" drive to the outlet village and the train ticket that suddenly looks reasonable. Change the trip length in the advanced options.
- Other costs and finance interest (advanced): parking permits, tolls, breakdown cover, cleaning and the interest on a loan or PCP are real costs most back-of-envelope sums leave out. Add them as annual figures and they join the fixed stack.
- Tyres and wear per mile (advanced): a set of tyres every 20,000 to 30,000 miles plus brakes and other mileage-related wear comes to roughly 2p to 5p a mile. It varies with distance, so it is added to the variable costs and to the marginal trip figure.
- Per month and fixed costs share (advanced): the annual bill in monthly terms and the proportion that is spent whether or not the car moves. On a typical car well over half the cost is fixed.
- Versus HMRC's 45p rate (advanced): how your true cost per mile compares with the approved mileage rate, and what that means in pounds a year on your mileage. Drivers of larger or newer cars are often out of pocket on business miles, since the rate has been frozen since 2011.
- Marginal cost of that trip (advanced): fuel and wear only. For an owner the extra weekend trip genuinely costs only this once the fixed stack is sunk, which is why per-mile figures serve ownership decisions and marginal figures serve trip decisions.
- Cost per mile at a different mileage (advanced): the fixed costs spread over a different number of miles. Low-mileage drivers pay the most per mile: a 3,000-mile-a-year car can quietly exceed GBP 1 a mile, the arithmetic behind every car-club and taxi-instead comparison, with the crossover usually in the 4,000 to 6,000-mile band.