Below is FFPrep’s Fantasy Football Trade Analyzer.
Just type in the players you are trading away on the left and the players you are receiving on the right and it will tell you how many points per game each player is projected to score over the remainder of the season (using their average PPG and the remaining opponents).
Remember this is a tool that assumes you are starting everyone involved. If you have Tom Brady and you are trading away Carson Palmer, the Trade Analyzer does not know that you have Brady and may give you results you didn’t expect. Use this as a tool, not an end-all-decision-maker.