Where the name "17c" comes from
The formula circulating today as "17c" is commonly associated with a 2001–2002 class-action settlement, Mabry v. State Farm Mutual Automobile Insurance Co., in Muscogee County, Georgia. That litigation is the most frequently cited origin point for the specific calculation structure (a base value, a percentage cap, and damage/mileage multipliers) that later spread into broader claims-industry use as a rough starting point for diminished-value discussions.
The calculation, step by step
- Start with pre-accident value — your vehicle's value immediately before the loss.
- Apply a 10% base value cap — the maximum possible diminished value is treated as 10% of that pre-accident value, regardless of damage severity.
- Apply a damage-severity multiplier — a fraction (commonly ranging from 1.00 for severe structural damage down to 0.00 for damage categories treated as having no measurable effect) applied to the capped value.
- Apply a mileage multiplier — a further fraction that reduces the result as mileage increases, reflecting that high-mileage vehicles are seen as losing comparatively less specifically from an accident history.
Worked example. Pre-accident value: $20,000. 10% cap: $2,000. A moderate damage multiplier of 0.50: $1,000. A mileage multiplier of 0.80 for moderate mileage: a final disclosed baseline of $800. Every substituted number in this chain is shown in the Diminished Value Baseline calculator's output — nothing is hidden inside a single final figure.
Why this site calls it a "baseline," never "true diminished value"
Because the formula is a commonly published convention, not a verified measurement of your specific car's actual value loss in your actual local market. The Georgia regulator directive above is explicit that no formula has been approved as determinative — meaning even in the state most associated with its origin, it is not treated as legally conclusive. This site presents the 17c-style result strictly as a transparent comparison baseline, and separately builds real market evidence from actual comparable listings — see Building Diminished-Value Market Evidence — rather than ever averaging the two into one number.
What this guide cannot tell you
It cannot tell you what multiplier values any specific insurer uses in practice (they vary), whether your state permits a first-party diminished-value claim at all, or what your vehicle's real diminished value is in your local market — only real comparable-sale evidence for your specific car can speak to that.