I believe there is a thrust calculator out there, but it is not as accurate as strapping a digital fish scale or similar to the tail and hitting the throttle, and that is not as accurate as just plain flying the plane and seeing how it pulls, feels, and accelerates out of a hover. I had a 50cc Yak that weighed 15 pounds and would show 24 pounds of thrust on a fish scale. You'd think that would be awesome, right? Wrong. The plane had barely enough power to pull out of a hover...
I can tell you that if you do rely on the fish scale method, expect 2:1 thrust to weight to have a decent-powered plane.