A quick and easy way of finding out the value of a salvage title vehicle is to contact your current insurance agent. Determining salvage value can be tricky, and while insurance companies have formulas for calculating the value of salvage title cars, the science is not exact. For a rough estimate on your own, find the fair market value for the vehicle from a site like Kelley Blue Book or NADA, then subtract about 75-80% of that value to get you in the ballpark. However, each insurance company expresses valuation in different ways, and value may be expressed as more or less than this example.
For more info, see A Rebuilt Car Title: Pros vs Cons