Your Car Does Not Have a Cost per Mile. You Do.

Ask what a car costs per mile and you get a number back with the car's name attached, as though it were a specification like curb weight or horsepower. It is not. It is a fraction, and you supply the denominator.

Two people can buy the identical car on the identical day, keep it the same five years, and pay 123.9¢ a mile and 40.2¢ a mile respectively. Neither is doing anything wrong. The difference is entirely how far they drove.

Why the fraction behaves that way

Every cost of owning a car falls into one of two piles, and the piles run on different clocks:

ACCRUE ON THE CALENDAR                ACCRUE ON THE ODOMETER
  depreciation                          fuel or electricity
  loan interest                         upkeep, repairs, tires
  insurance
  registration and taxes

  charged whether or not you drive      charged only when you do

The left-hand pile is the larger one for most drivers, and it does not care about your mileage. Park the car for a year and it still depreciates, still carries insurance, still accrues interest, still needs plates. Divide a fixed annual sum by a smaller number of miles and the per-mile figure climbs — not because the car got more expensive, but because there are fewer miles to spread it across.

This is not a quirk of the arithmetic. It is the single most important thing about cost per mile, and it is why a figure quoted without an annual mileage attached is not really a figure at all.

One car, six drivers

A worked example: a $24,000 car kept 5 years and sold for $11,000, financed with $3,800 of interest over the loan, insured at $1,650 a year, $220 in registration, $900 a year in upkeep, running on gasoline at $3.19 at 27 MPG.

At 12,000 miles a year, that is 60,000 miles and $37,739 in total — $7,548 a year, $629 a month, 62.9¢ a mile:

  depreciation    $13,000    21.7¢/mi   34%   calendar
  loan interest    $3,800     6.3¢/mi   10%   calendar
  insurance        $8,250    13.8¢/mi   22%   calendar
  registration     $1,100     1.8¢/mi    3%   calendar
  fuel             $7,089    11.8¢/mi   19%   odometer
  upkeep + tires   $4,500     7.5¢/mi   12%   odometer
  ────────────────────────────────────────────────────
  total           $37,739    62.9¢/mi

  69% of it accrues on the calendar, not the odometer.

Now change nothing except how far it is driven. Same car, same insurance, same loan, same purchase and resale:

  MILES A YEAR      COST PER MILE
     5,000           123.9¢
     8,000            84.7¢
    12,000            62.9¢     ← the car above
    15,000            54.2¢
    20,000            45.5¢
    25,000            40.2¢

  every row is the same car and the same money

A three-fold spread, from the same vehicle and the same spending. The driver at 5,000 miles a year is not being wasteful — they are spreading $5,230 a year of unavoidable ownership cost over very few miles. If anything the table is an argument about whether that person should own a car at all, which is a genuinely different question from which car to own.

What this does to the published averages

The best-known figure in this area is AAA's. Your Driving Costs, 2025 edition, puts the cost of a new vehicle at $11,577 a year, measured over five years at 15,000 miles a year — which works out to 77.2¢ a mile. The IRS standard mileage rate is 76¢ for July 1 – December 31, 2026. The two land close together, which is some comfort about both.

Both are honest and both are averages of a specific thing. AAA's covers a new vehicle, averaged across vehicle categories including pickups; their small sedan comes in at 55.87¢. And crucially, the 15,000 miles a year is part of the definition, not a detail — at 5,000 miles a year the same car would price far higher, and AAA would be the first to say so.

So the published number is a reasonable default for someone who drives roughly 15,000 miles a year in a roughly average new car. If that is not you — an older car, a paid-off car, a short-mileage year — it is the wrong number, and the direction of the error depends on which way you differ.

The line everyone optimises is not the big one

In the example above, fuel is 19% of the total — the third-largest line of six. Depreciation is 34% and insurance is 22%. AAA's breakdown says the same thing: depreciation $4,334 a year and finance charges $1,131, against fuel at 13¢ a mile.

This is worth sitting with, because attention does not distribute that way. Fuel price is posted in foot-high numerals on every corner and is paid in visible weekly instalments; depreciation is never invoiced and shows up once, years later, as a disappointing trade-in offer. The cost you watch and the cost you incur are close to inversely related.

The practical consequence: a driver who switches to a car 5 MPG better saves real money, but a driver who buys a car that holds its value better, or shops the insurance, is usually working on a larger line. Both are worth doing. Only one of them feels like it.

Which per-mile number to use for what

The total figure is the right answer to exactly one kind of question, and the wrong answer to another kind that looks similar.

Use the whole 62.9¢ when the car itself is in question: whether to own it, whether to own two, whether a job across the state is worth it, what to charge a business for mileage. These decisions change the fixed costs, so the fixed costs belong in the number.

Use the 19.3¢ variable rate when only the miles are in question and the car is a given: whether to drive to the coast this weekend, whether to take your car or a friend's. Charging that trip for a share of depreciation and insurance you would pay regardless is double-counting, and it will talk you out of things that are actually cheap.

The difference between those two rates is 43.6¢ a mile in this example — on a 600-mile round trip, the gap between $116 and $377. Using the wrong one is not a rounding error.

What the number cannot tell you

Resale value is a forecast. Depreciation is the largest line here and it is the only one you do not know until you sell. Every cost-per-mile figure, including AAA's and this site's, rests on an estimate of what the car will be worth at the end. Treat a result as provisional on that guess, and run it again at a resale value 20% lower to see whether your conclusion survives.

It is an average over the whole period, not a schedule. Depreciation is front-loaded and repairs are back-loaded, so the early years and late years of ownership do not each cost the average. A figure over five years is a fair summary of five years; it is not a prediction of next year.

It says nothing about whether you can afford it. A low cost per mile on a car with a payment you cannot meet is arithmetic that is true and useless. Car Affordability is the tool for that question.

Running it on your own car

Six figures, all of which you either have or can get in an afternoon: what you paid, what you think it will sell for, your total loan interest, your annual insurance premium, your registration, and a year of upkeep. Your real annual mileage comes off the odometer, and your real fuel economy comes from a fill-up, not the sticker.

True Cost per Mile assembles those into a total, breaks it by category, splits the calendar costs from the odometer ones, and re-divides the same figures at other annual mileages so you can see how much of your answer is about the car and how much is about you.

From there: the commute is usually the largest single block of those miles, Break-Even Mileage tells you whether a more efficient car repays its premium at your mileage, and the repair-or-replace question is where a per-mile figure does its most useful work — because a repair bill priced per mile is almost always smaller than it felt in the shop.