Can I put seven 12/2 cables in one 4 x 4 x 2-1/8 square metal junction box? According to some box fill calculators, this may be a tad too many wires for this junction box. However, I'm hoping I'm wrong. Other wise I may have to use two junction boxes.

Adding context: This junction box will serve 4 new closet lights and new light switches, along with an existing bathroom vanity light and switch and 4 existing recessed led lights (on one switch). Along with the power source line in, it is a total of seven 12/2 cables.

  • 1
    perhaps daisy chain some of the closet lights
    – Jasen
    Dec 28, 2022 at 11:55

1 Answer 1


12 AWG = 2.25" x 15 (14 conductors plus 1 for all the grounds) = 33.75"

In NEC 2020 (not adopted everywhere yet), every 4 grounds count as 1:

12 AWG = 2.25" x 16 (14 conductors plus 2 for all the grounds) = 36.00"

4" square 2.125" deep box I found listed as 30.3", which is less than 33.75". So it won't work.

Add a domed cover for another 7", total 37.3", and you are OK even with NEC 2020.

You can also use a 4.6875" (4-11/16") x 2.125" box sized at 42". That gives you room to spare - enough for one more cable.

I found a great PDF of box dimensions - not everything listed on Home Depot or other retail sites includes cubic inches.

  • 3
    The NEC 2020 rule is that grounds are 4 for the price of 1. So that would be 2 grounds. A domed cover may add enough cubic inches to make a difference. Dec 28, 2022 at 7:06

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