What is Diminished Value? In Layman’s terms, Diminished Value is the immediate loss of value your vehicle suffers due to an accident even when your vehicle has been repaired. This loss of value is created by Stigmas and damage that can not be restored to... I have people ask me all the time… Ken, can you show me how to calculate diminished value? To do a proper appraisal, it takes research. Research most other appraisers are not eager to do. Actually, I’m not even eager to do it, but I know it has to be done...