Salary Relative to Cost of Living Calculators
 
Hint:  Enter nearby large cities and consult more than one calculator for a better overall estimate.
 
Some of these sites also have additional tools of value for comparing overall quality of life factors.
Moving.com
Simplest of the calculators on this page.  Forensic Scientists can select the "Research & Science" field, then select the most similar job description.  
Bestplaces.net Salary Calculator
Even "from" DC it will ask you to also pick a city.
RelocationEssentials.com 
Shows easy to understand breakdown of food, housing, transportation costs, etc. 
Recommend clicking the "county" button and entering the county names below the state.

Salary.com
Minimal details, but nice graphic of salary vs. cost of living for comparisons.
CNN.com
City choices limited and difficult to pick-out from the odd by-state listing.


Google links to more good tools.