There are statics calculators available on the following webpage.
Beam Deflections and Stress Equations and Calculators
For simplicity, I recommend concentrating the load calculations at one point to compensate to the FOS.
Cantilevered Beam with Load at Location Between Support and Load Equations and Calculator
You could also use this Flagpole Base Design Calculator to determine the bearing loading in the ground.
Flagpole Base Design Calculator