It is difficult to prove exact diminished value for any one vehicle because placing a value on the vehicle will be a subjective assessment made by different individuals. The most effective way to calculate diminished value is to hire an expert specializing in this field. This is usually an expert in car pricing, local market demand, auction results, and repair costs, hidden damages to your vehicle, and a history with trial testimony. A simpler way is to obtain a print out or pricing sheet from the place in which you purchased the vehicle, which would include all the features, the costs associated with each, and the sale price. You can then request that the dealership calculate a new value based on the damage and repair to your vehicle. Once you have both, you can subtract the pre-collision value from the post-collision value and that is the diminished value of the car. You may also look at comparable vehicles to your own in the geographic area you are located.