Car Depreciation per Mile Calculator

Depreciation is the largest cost of running most cars and the only one that never sends a bill. It is settled in a single transaction years after it accrued, when the car is sold for less than it cost, which is precisely why it drops out of most per-mile figures. This calculator does the one piece of arithmetic that makes it visible: the loss in value divided by the miles that caused it.

At the defaults, a 30,000 car sold for 8,000 after 150,000 miles has lost 22,000, which is 0.147 a mile. That figure sits alongside fuel, maintenance, insurance and tax rather than replacing them, so an all-in cost per mile is several times larger. The useful comparison is against what a journey feels like it costs, since fuel alone is the number most people have in mind and it is only one of the components.

Depreciation is not linear, which this calculation deliberately ignores. The steepest loss comes early, so a car sold after three years will have shed a far larger share of its value than three tenths of its ten-year total. Averaging across the whole life suits a per-mile figure and suits a decision about when to sell far less, since for that the shape of the depreciation curve carries more information than its total.

Quick example

A 30,000 purchase, an 8,000 expected resale value and 150,000 lifetime miles: 0.15 a mile, from a total depreciation of 22,000, which is 73.33 per cent of the purchase price. The card rounds to two decimal places, so the underlying 0.147 shows as 0.15; at sub-unit figures that rounding is worth knowing about. A monthly figure on a ten-year assumption, 183.33, expresses the same loss as time rather than distance.

Which inputs matter most

Only the gap between the two prices matters, not their level: a 30,000 car resold at 8,000 and a 25,000 car resold at 3,000 both lose 22,000 and both give 0.147 a mile. Expected Lifetime Miles is the divisor, so it pulls the other way and hard, the same 22,000 over 250,000 miles coming to 0.088. Of the three, the resale estimate is the one nobody can know, which makes it the input worth testing at more than one value.

What's happening under the hood

Purchase price minus expected resale value, divided by expected lifetime miles. The result is an average: every mile is charged the same amount, from the first to the last. The monthly row divides the same total by ten years rather than by the miles, which is an assumption the calculator makes rather than something you enter.

Why see the number at all

Because the alternative is a per-mile figure built from fuel alone, which understates the cost of driving by a wide margin and flatters every comparison against public transport, cycling, or not making the trip. Depreciation does not feel like spending while it happens. It is spending, and this is the rate at which it happens.