Reviewed & approved by attorneys at Conduit LawDV calculatorFree valuationCall (303) 219-2052
PDPROPERTY DAMAGEKING
Check my claim

Diminished Value

The 17c Diminished Value Formula, Explained

When you raise a diminished value claim, many insurers reach for the “17c formula.” It produces a tidy-looking number — that usually lands well below what your car actually lost. Here's how it works and why.

Written by Elliot Singer, Esq.·Attorney-reviewed by Conduit Law·Updated June 2026
The short version
  • ✓The 17c formula caps diminished value at roughly 10% of a base value, then cuts it further.
  • ✓It reduces the number for mileage and for damage severity using fixed multipliers.
  • ✓Those assumptions are arbitrary and frequently understate a real loss.
  • ✓It's an opening offer — you can counter it with a market-based valuation.

What is the 17c formula?

The 17c formula is a widely used method for calculating diminished value. The name comes from how the approach entered common use through insurance-claim practice, and most insurers apply some version of it. The point to understand is what it does to your number — it caps it, then shrinks it.

How the 17c calculation works

The formula generally moves through three steps:

  1. Start with a base value. Usually a published market value for your vehicle.
  2. Apply a 10% cap. The formula caps the maximum diminished value at roughly 10% of that base — your loss can’t exceed this ceiling no matter the facts.
  3. Reduce for mileage and damage. Two multipliers then cut the capped figure further: one for your car’s mileage, another for the severity of the damage.
A quick example
A $30,000 car is capped at $3,000 (10%). Apply a mileage multiplier and a damage multiplier — each less than 1 — and that $3,000 can fall to $1,500, $900, or less. Meanwhile, the market may show the car actually lost far more.

Why 17c shortchanges you

The problem isn’t your car — it’s the formula’s assumptions. The 10% cap is arbitrary and isn’t tied to what your specific vehicle does in the real market. The mileage and damage multipliers compound the reduction, and together they can turn a genuine five-figure loss into a few hundred dollars. It looks objective because it’s a calculation, but every input is a choice that happens to favor the insurer.

What to do when you get a 17c offer

Treat a 17c figure as the opening offer it is. The stronger response is a market-based diminished value figure: a comparable-vehicle analysis that shows what cars like yours actually sell for, with and without an accident on record. That’s a number built from evidence rather than a capped table — and it’s what tends to move a lowball toward a fair result.

17c formula FAQ

What is the 17c formula?+
The 17c formula is a method many insurers use to calculate diminished value. It starts from a base value, applies a flat cap (commonly 10% of that value), then reduces the figure further based on mileage and the severity of damage. The result is usually a low number relative to the car's actual lost value.
Why is the 17c formula bad for claimants?+
Because its key assumptions are arbitrary. The 10% cap isn't tied to your specific vehicle's market, and the mileage and damage multipliers can shrink a real five-figure loss down to a few hundred dollars. It's a starting offer dressed up as a calculation.
Do I have to accept a 17c diminished value offer?+
No. The 17c number is the insurer's opening position, not a binding figure. You can counter it with a market-based valuation built from comparable vehicles, which typically reflects a higher, better-supported loss.
What's a better way to calculate diminished value?+
A comparable-vehicle analysis — looking at what cars like yours actually sell for, with and without an accident on record. That measures your real loss from the market instead of applying a capped formula.

Related diminished value guides

About the author

This guide is written by Elliot Singer, Esq., founder of Conduit Law and the attorney behind Property Damage King. PDK focuses on practical, document-backed insurance-claim reviews for diminished value, total loss, and related auto property-damage disputes.

Property Damage King is a DBA of Conduit Law. This page is attorney advertising and is provided for general educational purposes only — it is not legal advice and does not create an attorney-client relationship. Insurance and claim rules vary by state and by policy; for guidance on your specific situation, talk to an attorney. Settlement examples are real past results provided for illustration and are not a prediction or guarantee of the outcome of any future claim.