Your vehicle's value is determined by comparing your vehicle's condition to similar vehicles. This may include input from local auto dealers, private parties or recent sales which the adjusters use in their valuation. Condition, equipment and mileage differences are also taken into consideration.
In addition, your insurance company may use a computerized evaluation process to assist them in determining the value of your vehicle. Insurance companies purchase third party computer systems (like CCC) that help them estimate costs in automotive claims and collision repairs. Third party software supplies insurers with software and a database that helps determine the value of a vehicle based upon automating the claims process. These systems have databases and systems that contain benchmarking tools to find the true value of a vehicle from repair shops and dealers.
You can also visit some sites that allow you to find your cars estimated actual cash value:
Comment Update: For classic restored vehicles, you typically do not have an auto insurance policy that pays 'Actual Cash Value'. When a typical policy covers physical damage, it won't insure vehicles over a certain age (usually 20 years, sometimes less). For that reason, you purchase a 'stated value policy' for classic or restored vehicles. You and your agent determine the value that you want to be covered and your premium is based upon that. When a loss occurs, you are covered up to that stated value.
Comment Update: Between trade-in value and full retail is probably most closely associated with the actual cash value, but there is not a table to refer to, since it is specific to each claim and vehicle status.
There are too many variables for a simple answer to state an exact amount. When a carrer determines your ACV you can ask them what they used to determine this value. The purpose of reimbursing for your actual cash value is to pay you back and make you whole, so if the value determined seems unfair, you should dispute it with your claims adjuster and insurance company.