How to Calculate Diminished Value: The 17c Formula Explained
After an accident, your car is worth less on the resale market — even after a flawless repair — because the collision now sits on its vehicle-history report forever. Putting a dollar figure on that loss is what "calculating diminished value" means, and the most common method is the 17c formula. Here's exactly how it works, step by step, with a worked example you can follow.
In a hurry? The Diminished Value Calculator runs this same math for you instantly.
The 17c formula in four steps
- Find your pre-accident market value. Look up what your car was worth before the crash on Kelley Blue Book or NADA, matching the exact trim, options, and mileage. Everything else builds on this number.
- Apply the 10% cap. Multiply that value by 10% (0.10). The 17c formula assumes diminished value can't exceed 10% of the car's worth, so this is your ceiling. A $30,000 car → a $3,000 base.
- Apply the damage-severity factor. Multiply by a factor between 1.00 (severe structural damage) and 0.00 (no meaningful damage) — see the table below.
- Apply the mileage factor. Multiply by a mileage factor that shrinks as the odometer climbs, because higher-mileage cars lose proportionally less resale value from an accident.
Written as one line: Diminished Value = (Market Value × 0.10) × Damage Factor × Mileage Factor.
The 17c factors
Damage severity factor:
| Damage | Factor |
|---|---|
| Severe — structural / frame damage | 1.00 |
| Major — panels replaced, significant repair | 0.75 |
| Moderate — multiple panels, moderate repair | 0.50 |
| Minor — dents, scratches, one panel | 0.25 |
| Very minor — no meaningful repair | 0.00 |
Mileage factor:
| Mileage | Factor |
|---|---|
| Under 20,000 | 1.00 |
| 20,000 – 39,999 | 0.80 |
| 40,000 – 59,999 | 0.60 |
| 60,000 – 79,999 | 0.40 |
| 80,000 – 99,999 | 0.20 |
| 100,000+ | 0.00 |
A worked example
Say you have a $30,000 car with major damage (factor 0.75) and 35,000 miles (factor 0.80):
Enter your three numbers and get the 17c estimate instantly — free, no email.
Open the Diminished Value Calculator →The mistakes that quietly shrink your number
Because the 17c formula multiplies three inputs together, a small downward nudge to any one of them compounds fast — and adjusters know it. Watch for these:
- An understated pre-accident value. The 10% cap is built on your car's market value, so a low starting value shrinks everything below it. Insurers often quote a base value from comparables in worse condition or higher mileage. Pull your own KBB or NADA figure and local listings before you accept theirs.
- A downgraded damage severity. "Major" (0.75) versus "moderate" (0.50) is a one-third swing in your result. Structural or frame repairs, airbag deployment, and replaced panels support a higher factor — document them with the repair invoice.
- Treating the mileage factor as the whole story. High mileage does reduce the 17c number, but it doesn't cap what an independent appraiser can find — desirable models hold value despite the miles.
Does diminished value change by state?
The math is the same everywhere, but whether you can collect depends on your state. If another driver was at fault, their insurer generally owes diminished value in most states (a third-party claim). Claiming it from your own insurer (a first-party claim) is far more limited and often excluded — Georgia is the well-known exception that requires it, following Mabry v. State Farm. Confirm your state's rule before you count on a first-party payout; the full diminished value claim guide breaks this down.
When diminished value doesn't apply at all
Diminished value only exists if your car was repaired and kept. If the damage was severe enough that the insurer totaled the car, there's no repaired vehicle to lose resale value — you're owed actual cash value instead. Not sure which side of that line you're on? Check it with the total loss calculator first, then come back here if the car is repairable.
Now what?
A number on its own doesn't get you paid — you have to claim it. Once you have your 17c figure, the next step is filing the claim with the right insurer and countering the inevitable lowball offer. Our full guide walks through exactly how: How to File a Diminished Value Claim (and Beat the Lowball Offer).
Disclaimer: This explanation is educational and uses the industry-standard 17c formula. It is not an appraisal or legal advice, and actual diminished value depends on your vehicle, local market, and state law. For a binding figure, consult a licensed appraiser.