The basic idea
Two identical cars, same year/mileage/trim — except one has a clean title history and one has an accident and repair on its vehicle-history report (Carfax, AutoCheck, etc.). Buyers and dealers routinely pay less for the second one, even when the repair was done perfectly. That gap is diminished value.
Two different kinds of DV
"Diminished value" gets used loosely, but it actually describes two different situations — see Inherent vs. Repair-Related Diminished Value for the full distinction. In short: inherent DV is the value lost just from having an accident on the record, regardless of repair quality. Repair-related DV is additional value lost from a repair that was incomplete, used non-OEM parts, or wasn't done to the vehicle's original standard.
Two ways to think about measuring it
There are two genuinely different approaches, and this site deliberately keeps them separate rather than blending them into one number:
- A disclosed formula baseline — a transparent, published calculation (the "17c-style" formula) that starts from your car's pre-accident value and applies fixed percentage caps and multipliers for damage severity and mileage. See the 17c formula guide for its real origin and limits.
- Real market evidence — actual sale prices of comparable clean-title vs. accident-history vehicles, which shows what buyers in your specific market actually pay for the difference. See building market evidence.
What this guide cannot tell you
It cannot tell you whether your state recognizes first-party diminished-value claims (some do not, or limit them significantly), or what your specific vehicle's diminished value actually is. Both depend on your state's law and real market evidence for your car.