I think you are talking about depreciation. I depends on several factors like the car's make or model, age, overall condition, market demand, maintenance, and it's past (if involved in any crash, collision or not).
Generally a car loses 15 - 20 percent of it's value in a first year, then that much of it's value the next each years, like compound interest, but reverted :D.
So unless there's something special about your car, or there's something really special about your car that people looks for, that's how much it's going to depreciate.