How do you calculate load on steel beams?

try this website it might help - http://www.engineeringtoolbox.com/beams-support-forces-d_1311.html first off the calculations are based on beam size (example w14x26 [14=14" x26=lbs. ) which is around 5 3/16" wide x 13 7/8" high the flange thickness is around 3/8" thick and the web would be 1/4" wide you also must check the span and application (concrete Pier's, or schedule 40 columns (1/4" thick steel column) there are other factors which are involved in other words consult your engineer