Diminished Value (17c) Calculator
Estimate what your car's resale value dropped after an accident, using the industry-standard 17c formula — the same starting point insurers and independent appraisers use.
Short answer
Diminished value is the drop in a car's resale value after an accident, even after a good repair. Insurers often start with the 17c formula: 10% of the car's pre-accident value, cut by a damage factor and a mileage factor. It is usually claimed from the at-fault driver's insurer; only a few states allow it against your own.
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After a repair, a car carries an accident history that most buyers and appraisal guides discount, even when the repair is invisible. Diminished value is the dollar difference between what your car would have sold for with a clean history and what it’s worth now, with an accident on record.
The 17c formula, from the 2001 Georgia case Mabry v. State Farm, is the most commonly referenced starting point: it caps the base loss at 10% of the vehicle’s value, then reduces that by a damage-severity factor and a mileage factor. Insurers frequently use it (or a close variant) as their opening number.
How to strengthen a diminished value claim
- Get a repair invoice that clearly documents the extent of the damage.
- Consider an independent appraisal if the 17c number feels low relative to comparable vehicle listings.
- Check whether your state allows first-party diminished value claims before filing against your own insurer.
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Worked example
A sedan worth $24,000 before the crash, with 32,000 miles and moderate damage to structure and panels:
- 10% cap: $24,000 × 10% = $2,400
- Damage factor (moderate): $2,400 × 0.50 = $1,200
- Mileage factor (20,000–39,999 miles): $1,200 × 0.80 = $960
The 17c estimate is $960. The same car with 12,000 miles and major damage would come out at $2,400 × 0.75 × 1.00 = $1,800. If the car already had accident history before this crash, expect the insurer to argue for less. There is no standard deduction for that, so ask them to show how they got their number.
Treat the result as a floor for your negotiation, not a ceiling. On newer or low-mileage cars, an independent appraisal based on real resale comparisons often supports a higher number.
Frequently asked questions
What is the 17c formula?
The 17c formula comes from Mabry v. State Farm (Georgia, 2001) and estimates diminished value as 10% of the vehicle's value, adjusted down by a damage-severity multiplier and a mileage multiplier. It's widely used by insurers as a starting baseline.
Is the 17c number the most I can claim?
No. It is a conservative baseline. An independent appraisal that looks at actual comparable sales of similar vehicles with and without accident history often supports a higher number, especially on newer or low-mileage vehicles.
Can I claim diminished value from my own insurance company?
It depends on your state and your policy. Some states allow first-party diminished value claims, others only allow you to claim it from the at-fault driver's insurer (a third-party claim), and a few restrict it entirely.
Can I claim diminished value if the accident was my fault?
Usually not. Diminished value is normally claimed from the at-fault driver's insurer. Georgia is the best-known exception, where policyholders can recover diminished value from their own insurer. Check your state's rules and your policy wording.
How long do I have to file a diminished value claim?
You are generally limited by your state's statute of limitations for property damage, which differs by state. Insurers also expect the claim reasonably soon after repairs are finished, so file once you have the final repair invoice.
What evidence makes a diminished value claim stronger?
The final repair invoice showing the extent of the damage, photos, the vehicle history report showing the accident, and either comparable listings or an independent appraisal showing how accident history lowers resale value for your model.