How do I determine the fill rating of a conduit?
All conduit has a fill rating (which equates to 40 % of the free area full of wire, unless there are only 1 or two wires - in practice, less fill is better - the full-rated fill is VERY hard to pull into conduit. That is slightly different for different type conduits due to the different actual size of the hole in the different types of conduit. There are charts in the NEC, and there are also a LOT of on-line conduit fill calculators (and some charts.)