The 17c Formula: How Insurers Calculate Diminished Value — and Why It Underpays

Updated July 2026 · Reviewed by the PayoutJet claims team

If you've filed a diminished value claim and received an offer that felt insultingly small, there's a good chance a spreadsheet produced it in seconds using the 17c formula. It's the auto insurance industry's standard method for calculating DV, it's used on claims in all 50 states, and it has one consistent property: it produces numbers far below what the used-car market says your vehicle actually lost.

Where 17c came from

The name refers to paragraph 17(c) of the class-settlement documents in Mabry v. State Farm, the 2001 Georgia Supreme Court case that forced insurers to assess diminished value on Georgia claims. As part of administering thousands of settlement claims, a formula was adopted for bulk processing. It was never enacted as law, never validated against market data, and never intended as the universal measure of diminished value — but it spread through the industry precisely because it's fast, uniform, and cheap. A quarter century later, adjusters nationwide still cite it as if it were authoritative. It isn't: no statute or regulation in any state requires it, and courts are not bound by it.

How the math works

The formula runs three steps, each of which can only shrink your recovery:

1. Start with a 10% cap. Take the vehicle's pre-accident value (usually the NADA/book value) and multiply by 0.10. Whatever your car actually lost, the formula assumes it can never exceed 10% of its value.
2. Multiply by a damage modifier. From 1.00 for severe structural damage down to 0.25 for minor panel damage and 0.00 for no structural involvement. Cosmetic-but-recorded accidents can compute to near zero even though the history report still scares buyers.
3. Multiply by a mileage modifier. 1.00 under 20,000 miles, stepping down to 0.00 at 100,000+. This is applied even though the book value in step one already accounts for mileage — the same penalty counted twice.

A worked example

So the insurer offers $960. Meanwhile, dealers and private buyers looking at that same SUV's accident-flagged history report will commonly discount it by 10–20% of its value — $2,400 to $4,800 — and some dealers will only take a structurally repaired vehicle at wholesale. The formula's answer and the market's answer aren't in the same neighborhood.

The three built-in flaws

How to counter a 17c offer

1. Get the offer and its basis in writing. Ask the adjuster to state the methodology. Once "17c" is on paper, you can attack the method rather than haggle over the number.
2. Answer with market evidence. Comparable listings of your vehicle with clean vs. accident history are the direct measurement of your loss. The written question that moves claims: "Please explain why actual market data for this vehicle should be disregarded in favor of an administrative formula that no law in this state requires."
3. Cite your state's real standard. The legal measure of your loss is the difference in fair market value before and after the accident — not a formula output. Deadlines and specifics vary; check your state in our state-by-state guides.
4. Escalate if the formula is the final answer. Supervisor review, an insurance-department complaint, or small-claims court — where a judge will hear market evidence, not modifier tables. Send everything with a formal demand letter.

PayoutJet is a technology company, not a law firm; this article is general information, not legal advice.