Determining your car's worth is somewhat like an insurance company calculating a vehicle's actual cash value (ACV) after a total loss. To valuate your vehicle you need to determine what amount you could get if you were to trade-in or sell your vehicle at this point in time.
You can use valuation tools, such as used car guides created by NADA, Edmunds or Kelley Blue Book (KBB). These guides will typically give you trade-in values, retail values and private party values. To get the most accurate idea of what your vehicle is worth put in what options your car has, the mileage and basic condition (before the accident if you are looking for the ACV after an incident).
If you are trying to determine how much an insurance company will offer you as a settlement for ACV, then Kelley Blue Book notes that insurance company policies vary quite a bit, but generally insurance adjusters try to determine the replacement value for a vehicle that has been totaled as a value somewhere between wholesale and retail.
KBB goes on to state that insurance companies also research comparable vehicles that have sold in your area to help determine a fair price. You could average the trade-in value with the suggested retail of your vehicle and use the resulting value as a reference point for determining replacement value.
Beyond these valuation guides you can look at how much a vehicle in your condition and mileage is selling for inyour local car market. Sites such as Autotrader might help you in this task. Once you have determined the value of your vehicle, you have the personal decision of if you want to carry physical damage coverages of comprehensive and collision coverage on the vehicle (if the car hasn't yet been in an accident, you can't add the coverages to to cover an accident that has already taken place).
Collision and comprehensive are needed as part of your car insurance policy if you want the ability make claims against your own policy when your car is damaged. If your car is ever totaled out, your insurer would pay you actual cash value for the car, so its important to know the value of your car to make sure it's worth placing these coverages on it. (See "Is it time to drop comp and collision?")
If you are wondering specifically how insurance companies determine ACV, then it can be difficult since insurance carrier's methods vary. However, the typical ways in which a claims adjuster will calculate the actual cash value are: comparing your vehicle to local sales of the same model car in similar condition and with similar mileage, using Kelley Blue Book or NADA guide values and/or a computerized evaluation process.
Use our insurance coverage calculator if you are trying to determine what insurance types and coverages are best for you and your current vehicle. You then can compare insurance companies to find the most affordable rates for your needs.