What is the aproximate load capacity of an 8″ I beam over a 20′ span.

What is the aproximate load capacity of an 8" I beam over a 20' span.

You haven’t included enough info for me to help you get the answerm but hopefully these two links will enable you to figure it out..

You’ll need to visit two sites. This one for the beam properties:
http://efunda.com/math/areas/IbeamIndex.cfm

And this one for a calculator:
http://efunda.com/formulae/solid_mechanics/beams/casestudy_bc_simple.cfm

Hope this helps.