NEC Table 370-16(a). Metal Boxes |
Number of Conductors in Outlet, Device,
and Junction Boxes |
Box Dimension
in Inches
Trade Size
or Type |
Minimum
Capacity
(in.3) |
Maximum Number of Conductors |
No. 18 |
No. 16 |
No. 14 |
No. 12 |
No. 10 |
No. 8 |
No. 6 |
4 X 1-1/4 round or octagonal
4 X 1-1/2 round or octagonal
4 X 2-1/8 round or octagonal |
12.5
15.5
21.5 |
8
10
14 |
7
8
12 |
6
7
10 |
5
6
9 |
5
6
8 |
4
5
7 |
2
3
4 |
4 X 1-1/4 square
4 X 1-1/2 square
4 X 2-1/8 square |
18.0
21.0
30.3 |
12
14
20 |
10
12
17 |
9
10
15 |
8
9
13 |
7
8
12 |
6
7
10 |
3
4
6 |
4-11/16 X 1-1/4 square
4-11/16 X 1-1/2 square
4-11/16 X 2-1/8 square |
25.5
29.5
42.0 |
17
19
28 |
14
16
24 |
12
14
21 |
11
13
18 |
10
11
16 |
8
9
14 |
5
5
8 |
3 X 2 X 1-1/2 device
3 X 2 X 2 device
3 X 2 X 2-1/4 device
3 X 2 X 2-1/2 device
3 X 2 X 2-3/4 device
3 X 2 X 3-1/2 device |
7.5
10.0
10.5
12.5
14.0
18.0 |
5
6
7
8
9
12 |
4
5
6
7
8
10 |
3
5
5
6
7
9 |
3
4
4
5
6
8 |
3
4
4
5
5
7 |
2
3
3
4
4
6 |
1
2
2
2
2
3 |
4 X 2-1/8 X 1-1/2 device
4 X 2-1/8 X 1-7/8 device
4 X 2-1/8 X 2-1/8 device |
10.3
13.0
14.5 |
6
8
9 |
5
7
8 |
5
6
7 |
4
5
6 |
4
5
5 |
3
4
4 |
2
2
2 |
3-3/4
X 2 X 2-1/2 masonry
box / gang
3-3/4 X 2 X 3-1/2 masonry
box / gang |
14.0
21.0 |
9
14 |
8
12 |
7
10 |
6
9 |
5
8 |
4
7 |
2
4 |
