Wow! I was struggling with Xerox's paper types and weights tables, expressed in grammage (gsm), in the User Guide. Fortunately, for a novice like me, I stumbled into a great app, from Case Paper, that converts between basis weight and grammage (among other features) for various paper grades. I am not affiliated with Case Paper, but I sure do appreciate them.
----- ColorQube 8580dn | Snow Leopard System 1.3.8.P / OS 10.80 / PS 4.19.0 / Eng 26.P18.104.22.168 / Net 44.38.01.12.2015