I'm a metal fabricator designing some furniture of welded steel. I am not an engineer, but would like to do this right! Where do I begin if I want to calculate deflection under load of cantilevered members and spanning members? I want to avoid the custom-furniture-builder traps of...

A) under-building and winding up with a springy table and

B) over-building and making my furniture far heavier than it needs to be.

I'm somewhat experienced with CAD. Is there any easy-to-use software in which to draft my designs and subject them to abuse? A series of formulas I can use for reference?