Last updated · By Mustafa Bilgic
How this calculator works
The arithmetic is intentionally simple and auditable:
(Pre-accident fair market value − post-repair fair market value) × recoverable share = estimated recovery.
If a well-supported pre-loss value is $30,000 and a post-repair appraisal is $26,500, the inherent loss is $3,500. At a modeled 80% recoverable share, the estimate is $2,800. Repair cost is not used as a proxy: a $12,000 repair does not prove the market fell by $12,000, and a lower repair bill does not prove there is no stigma loss.
How to prove pre-loss and post-repair value
| Value question | Useful evidence | Common mistake |
|---|---|---|
| Pre-accident value | Local comparable sales for the same year, make, model, trim, mileage, options and condition. | Using an asking price for a different trim or unusually low-mileage car. |
| Quality of repair | Final invoice, scan/alignment records, OEM procedures, structural measurements and photographs. | Claiming inherent loss before repairs are complete and inspected. |
| Post-repair value | Independent appraisal and written dealer trade-in opinions identifying the accident-history deduction. | Using a verbal opinion with no comparable market support. |
| Accident history | Vehicle-history report, damage disclosure and repair severity. | Ignoring prior accidents, title issues or pre-existing damage. |
Use several genuine comparables and keep screenshots with the date, VIN or listing identifier and location. A qualified appraiser should explain adjustments rather than simply announce a number.
Which kind of diminished value are you claiming?
- Inherent diminished value: the market loss remaining after competent repairs because the vehicle now has an accident history.
- Repair-related diminished value: loss caused by incomplete or poor repairs, mismatched paint, remaining frame problems or non-equivalent parts.
- Immediate diminished value: the theoretical difference immediately after damage and before repair; it is less often the measure pursued in an ordinary post-repair claim.
This calculator is designed for inherent diminished value after repairs. If repairs remain defective, document that problem separately and use the correct repair or warranty process.
Who is the claim made against?
Diminished value is commonly presented as a third-party property-damage claim against the at-fault driver's carrier. Whether your own collision policy pays diminished value is controlled by the policy and state law; some policies exclude it. The Washington State Office of the Insurance Commissioner advises consumers that diminished value is typically claimed against the at-fault party's insurer, that some own policies do not cover it, and that the claimant must prove the market decrease.
Notify the insurer, complete repairs, gather the valuation package and ask for the written basis of any rejection or alternative number. Do not combine a property-only resolution with a release of an unresolved bodily-injury claim.
Claim package checklist
- Liability acceptance or evidence showing the other driver caused the collision.
- Pre-accident photos, service history and condition/mileage records.
- Complete repair estimate and final invoice, including supplements.
- Post-repair inspection and, where justified, independent appraisal.
- Matched local comparables before and after accident-history adjustment.
- Vehicle-history report and written trade-in or dealer evidence.
- A concise calculation, amount requested and copies of every exhibit.
For the wider collision file, use the claim evidence checklist. If an unidentified driver caused the damage, see the hit-and-run coverage guide.
Factors that can reduce or defeat a claim
- Very high mileage, poor pre-loss condition or a vehicle near the end of its economic life.
- Prior accidents, title brands or unrepaired earlier damage.
- Minor cosmetic damage with no supported market effect.
- Incomplete repairs or a valuation obtained before repairs finish.
- No liability against the target driver or a comparative-fault reduction.
- A first-party policy exclusion or a state rule limiting the route claimed.
- Evidence based only on generic percentages rather than the local market.
Frequently asked questions
How is diminished value calculated?
The economic starting point is fair market value immediately before the loss minus fair market value after complete repairs. This calculator uses those two evidence-based inputs and can apply a recoverable share.
Can I claim against my own insurer?
Often the claim is made against the at-fault driver's insurer, while first-party coverage depends on the policy and state law. Some policies exclude or limit diminished value. Read the contract and state guidance.
What proves the loss?
Useful proof includes accurate pre-loss comparables, a post-repair appraisal, supported dealer opinions, repair and structural records, photographs and a vehicle-history report.
Is the 17c formula required?
There is no single nationwide formula. Ask how any insurer method reflects the vehicle's actual local market. This calculator uses observed pre-loss and post-repair values instead.
Authoritative consumer source
Washington State Office of the Insurance Commissioner: Filing an auto insurance claim includes current diminished-value guidance.