What can I exspect to pay for a used car in one year?

What I'm really trying to ask is I need to find a website or something that can estimate what a cars value will be in the future. Thanks|||Go to kbb.com and look up the car's value now, then look up the value for the same car but one year older and about 15,000 more miles. The difference would be the approximate amount by which the car depreciates in value in one year.