How Is Diminished Value Calculated?
Diminished value is best calculated by comparing your repaired car against real market listings of similar vehicles with and without accident histories; the insurance industry's "17c" formula is a shortcut that usually understates the true loss.
The 17c formula (and why insurers like it)
The most cited method is the "17c" formula, which comes from a Georgia class-action settlement (Mabry v. State Farm). It starts from a base value — capped at 10% of the car's pre-accident value — then multiplies by a damage severity factor and a mileage factor. Insurers favor it because the 10% cap and the mileage multiplier keep payouts small and predictable.
- Base loss = 10% of the vehicle's pre-accident value (a hard cap).
- × a damage multiplier (0 to 1) based on severity.
- × a mileage multiplier (0 to 1) that shrinks the number as miles climb.
Why 17c usually understates the loss
The formula's inputs are essentially arbitrary. The flat 10% cap has no basis in how any particular market prices accident history, and the mileage multiplier can zero out a legitimate loss on a car that still has plenty of life left. Two cars with the same 17c score can lose very different amounts in the real world. It's a negotiating anchor for insurers, not a measurement of your actual loss.
The market-comparison method
A more defensible approach is to look at what the market is actually paying. You compare your specific vehicle — year, make, model, trim, mileage, options, and region — against real listings and recent sales of similar vehicles, some with clean histories and some with reported accidents. The difference between the two groups is a grounded estimate of your diminished value, backed by evidence an adjuster can see rather than a formula they can wave away.
- Establish your car's pre-accident market value from comparable clean-history vehicles nearby.
- Find comparable vehicles that carry a reported accident on their history.
- The gap between those two, adjusted for mileage and condition, is your estimated diminished value.
This is the approach CarAccidentValuation uses: it pulls real comparable listings in your area so your number is tied to the market, not a capped formula.
What moves the number
- Pre-accident value — higher-value cars have more value to lose.
- Severity and type of damage reported (structural/frame damage hurts most).
- Age and mileage — newer, lower-mileage cars lose more.
- Make and model desirability and how the local market prices history.
See real comparable listings near you in about a minute. No account, no credit card.
Get startedFrequently asked questions
- Do I have to accept the insurer's 17c number?
- No. The 17c formula is a negotiating position, not a legal requirement. You can present your own market-based evidence and dispute a lowball figure.
- Is a higher-value car worth more in diminished value?
- Generally yes — a car with more pre-accident value has more value it can lose, so higher-value vehicles tend to have larger diminished value claims.
- Does high mileage kill my claim?
- Under the 17c formula the mileage multiplier can shrink the number sharply, but a market comparison may still show a real loss. Mileage matters, but it shouldn't automatically zero out a legitimate claim.
This guide is general information, not legal advice. Rules, deadlines, and eligibility for diminished value and total-loss claims vary by state and by insurance policy.