How to calculate the cross section of splice/tap

[Jin Kim]

Just want to check out how do we literally calculate the cross section of the "splice/tap"
Sorry for the novice inquiry, but from wireway article 376.56 (NEC 2020) I see following requirement.

"Splices and taps in metal wireways must be accessible, and they are not permitted to fill the wireway to more than 75 percent of the wireway’s cross-sectional area."
How do we actually calculate the cross section of a splice/tap?

for example suppose we have;
a) 3" x 3" wireway = 9 sqin
b) (10) 14 THHW wires (csa 0.0139 sq.in each) = 0.139 sqin
c) splice kits for (6) THHW wires = How do we calculate this part?

 

[LarryFine]

Simple measurement? Staggered positioning minimizes crowding.

It's almost impossible to actually fill a wireway to 75% of capacity.

 

[infinity]

Larry nailed it. Although the 75% rule is in the NEC I don't think that you couldn't exceed it if you tried so for all intents and purposes it can be ignored.