What this calculator does, and what it cannot do
It does: take your repair facts, your car and your ZIP code, compare them against local listings for the same vehicle, and produce a point estimate inside a range. It also runs the short formula most insurers open with, so you see both numbers side by side.
It cannot: inspect your car, or know what your insurer will decide. This is an estimate, not an appraisal or a promise of payment. It's based on the information you entered and general market data. Insurers may dispute or deny claims.
It also cannot help everyone. If the accident happened in a state where these claims generally do not work, if you were at fault, or if you signed a full release, the calculator says so on the spot and never takes you to a payment screen.
What you need before you start
Nothing except the repair facts, which you probably already know: the state and rough date of the accident, the car's year, make and model, the mileage, and how bad the damage was.
"I don't have the repair total yet" is a fine answer. If the invoice is still with the shop, pick the description that matches the damage instead. The calculator assumes a typical repair cost for that description, returns a wider range, and says on the report that the repair total was not supplied. Adding the invoice later narrows the range.
Almost every other question has an "I don't know" option. Only five things are required: the accident state, the accident date, fault, the vehicle, and the mileage.
The ten questions, in plain language
- Where did the accident happen? The state where it happened sets the rule and the deadline, not the state you live in.
- Who was at fault? The other driver, both of you, you, or not decided yet.
- When did it happen, and have you signed anything that closes the claim? Month and year is enough.
- Are you claiming from the other driver's insurer or your own? "Not sure" is allowed.
- Which car was damaged, and who owns it? Year, make and model, or the VIN. Owned, financed or leased.
- Mileage at the time, and the ZIP where the car is kept. Close is fine; the ZIP finds local listings.
- Which parts were damaged, and how bad was it? Front, rear, sides, roof, underbody — then cosmetic, moderate, major or severe.
- Frame or structural work, airbag deployment, sensor recalibration? "I don't know" counts as no, never as yes.
- The repair total, supplements, how it looks now, earlier accidents, whether this one shows on Carfax. All optional.
- What it was worth before, days without the car, whether a rental was covered. Optional, and they sharpen the number.
Nothing about your insurer, claim number, documents or photos is asked here.
The gap: the insurer's formula versus a documented estimate
Most insurers open with a short formula, often called 17c: ten percent of the car's pre-accident value as a ceiling, multiplied by a damage band, then by a mileage band that falls with every step and reaches zero above 100,000 miles. It is fast, it is fixed, and it never looks at what buyers in your area actually pay for a car with an accident on its record.
On one of our sample cases — a 2022 RAV4, rear damage, $7,200 repair — the typical insurer formula produced $887 and the documented estimate was $2,750. _Example, not a promise._
That gap is what the argument is about, and you cannot argue it with nothing. Across our four worked examples the estimates run from $1,800 to $12,250, depending on the car and the damage. _Examples, not promises._
How the estimate is computed
We start from what your car was worth immediately before the accident, built from listings for the same year, make, model and mileage band near your ZIP code. We then apply a loss rate that rises with the size of the repair relative to that value, and adjust it for the severity signals you reported — structural work, airbag deployment, sensor recalibration — plus age, mileage, vehicle segment, earlier accidents, repair quality and whether the accident is already visible on a history report. Where we find enough local listings of the same model both with and without an accident on record, we blend the observed price gap between them into the figure, weighted by how many listings there are, so a thin sample barely moves the number. The result is a point estimate inside a range, and that range widens when you tell us less.
The full method and its limits are on the methodology page. New to the term? Start with what diminished value is; for what happens after the number, see how to claim it.
Questions
Is the diminished value calculator free?
Yes. The estimate, the range, the insurer-formula comparison and your state's deadline cost nothing.
Do I need an account or an email address?
No account. We do ask for an email address on the first screen, because that is where we send your estimate. We also send occasional tips about diminished value claims, which you can unsubscribe from in one click.
How accurate is it?
Accuracy depends on what you can tell us. With the real repair total and enough local listings for your model, the range is tight; with a damage description instead of an invoice, the calculator returns a wider range and labels it. It is not an inspection, and no estimate can predict what an insurer will decide.
Does KBB show diminished value?
No. Kelley Blue Book and similar guides publish what a normal example of your car is worth. They do not price the accident on your car's record, which is the whole question here. A guide value is a starting point for the "before" number, and the calculator uses one when local listings are too thin, but it is not a diminished value figure.
Does Carfax matter?
Yes, and it is one of the questions. What buyers see is what moves the price, so whether the accident already appears on Carfax or AutoCheck changes the estimate. Carfax does not publish a diminished value number either; it records the event that causes the loss.
How long does it take?
About 90 seconds across six short screens. Answers save as you go, so you can close the tab and come back.