Repair or Replace Calculator

How this is calculated

Two ways of having a working car for the next stretch, priced over the same months and the same miles, then subtracted. Nothing more complicated than that — the difficulty in this decision has never been the arithmetic.

miles          = miles per year × (months ÷ 12)

repair per mile = repair bill ÷ miles          ← the headline

KEEP IT
  outlay       = repair + fuel + insurance + upkeep + registration
  net          = outlay − what it's still worth at the end

REPLACE IT
  outlay       = price + loan interest − this car sold as-is
                 + fuel + insurance + upkeep + registration
  net          = outlay − what the replacement is worth at the end

the answer     = the smaller net

The fuel line on each side is the division the rest of this site is built on: $ per gallon ÷ miles per gallon, or $ per kWh ÷ miles per kWh. Both cars get their own, because they are not the same car — an old one usually drinks more, and a replacement may not burn gasoline at all. The interest figure is the interest over this window only, not over the whole loan; the Auto Loan Payment Calculator prints both.

The one rule this page is built to contradict

“Never spend more on a repair than the car is worth.” It is the most repeated sentence in this decision, and it compares two figures that answer different questions. What a car is worth is the price of selling it. What a repair costs is the price of keeping it. A car's market value is set by what someone else would pay to take on its remaining life — which is exactly the thing you are about to buy, cheaper, by fixing it.

The result panel prints that ratio anyway, labelled, because you will be told it by someone before this is over and it is better seen than argued with. In the worked example this site uses, the repair costs 1.33× the car's value and keeping it is still the cheaper path by more than $6,000 over three years. The rule is groping toward a real question — how much longer will it last? — and never asks it. This page asks it, puts it in a field, and then shows you how much the answer moves if your guess is wrong by half.

The as-is value, and the dollar that gets counted twice

What the broken car would fetch today appears in exactly one place: as cash coming in on the replace side. That cash only arrives if you actually sell it. Counting it on the keep side as well — as a “loss” you suffer by not selling — is the commonest way this comparison is got wrong, and it always tilts the answer toward buying. The same discipline governs the two end values: each side is charged for what it spends and credited for what it still owns at the end, once.

Why the headline is per mile, not a verdict

The repair bill divided by the miles it buys is the only figure on this page that rests on no forecast at all. A written estimate is a known number and your annual mileage is a known number, so the division is exact. Everything else — both end values, next year's upkeep, how long the car has left — is an estimate, and the further down the page a figure sits, the more of them it carries. That is why the sensitivity strip moves the months rather than the money: if the repair still looks cheap at half your estimate of its remaining life, your guess is not carrying the decision and you can stop refining it.

The sources

What a replacement costs to own. AAA has published Your Driving Costs annually since 1950. Its 2025 edition put the average cost of a new vehicle at $11,577 a year, of which $4,334 was depreciation alone — the largest single category, and larger than fuel, insurance and maintenance put together for most vehicles. That figure is why a repair bill so often wins this comparison: an old car has already taken its depreciation, and the bill in your hand is visible in a way that $361 a month of quiet value loss never is. AAA is quoted here for scale and for its category list; none of its numbers enter your arithmetic, because a 45-model national average is a benchmark and not your car.

Why there is no threshold table on this page. The federal government answers “when should a car be replaced?” with exactly such a table. Under the Federal Management Regulation, 41 CFR 102-34.270 sets minimum retention standards for government vehicles — sedans and station wagons at “3 years or 60,000 miles”, four- and six-wheel-drive vehicles at 6 years or 40,000 miles, with the note that the standards are “stated in both years and miles; use whichever occurs first.” The companion section defines these as the “minimum number of years in use or miles traveled at which an executive agency may replace” a vehicle. It is a floor for a fleet, not advice for a driver, and it exists because nobody can inspect several hundred thousand vehicles one at a time. You can inspect yours. You have an estimate in your hand, you know what else the mechanic found, and you know your own mileage — which is strictly more information than any age-and- mileage cutoff can use. That is the whole reason this page is a calculator and not a rule.

How normal this decision is. S&P Global Mobility's annual vehicle-age analysis put the average age of the 289 million light vehicles on US roads at 12.8 years in 2025 — 14.5 years for passenger cars, an eighth consecutive annual rise, against a scrappage rate of 4.5%. The average car on the road is well past the age at which this question starts getting asked, and most of the people asking it are keeping the car.

What this does not cover

Risk, which is the real reason people replace cars. Every figure here is a middle expectation. It cannot price the spread around it, and an old car's spread is wider: usually it costs what you entered, occasionally it strands you. Read the gap between the two paths as what you are being paid to carry that risk, and decide whether it is enough — that judgment is yours, and it depends on things a calculator cannot ask, like whether there is a second car in the driveway.

Whether the repair is a good repair, or the car is safe. This is a cost comparison and nothing else. It does not know whether the estimate is fair, whether the part will hold, or whether the car should be on the road. A mechanic answers those, and a second written estimate is the cheapest thing you can buy in this whole process.

Also excluded: the time value of money — a dollar spent today and a dollar spent in year three are treated as the same dollar, which slightly favours the path that spends later. Inflation on any figure, likewise: fuel, premiums and repair labour all move, and everything here is held flat. And your time — days without a car, and hours at a shop, are real costs on the keep side that this page does not count.

Last reviewed: August 2026