Electrical nonmetallic tubing (smurf tube) fill chart
The most THHN wires of one size each ENT size may hold, with three or more wires at 40 % fill. Pick a size for XHHW-2 and THW as well.
| Trade size | Inside area | 40 % | #14 | #12 | #10 | #8 | #6 | #4 | #2 | #1/0 | #4/0 | 250 kcmil | 500 kcmil |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 0.285 | 0.114 | 11 | 8 | 5 | 3 | 1 | 1 | 1 | 0 | 0 | 0 | 0 |
| 3/4" | 0.508 | 0.203 | 21 | 15 | 9 | 5 | 4 | 1 | 1 | 1 | 0 | 0 | 0 |
| 1" | 0.832 | 0.333 | 34 | 25 | 15 | 9 | 6 | 4 | 3 | 1 | 1 | 1 | 0 |
| 1-1/4" | 1.453 | 0.581 | 60 | 43 | 27 | 16 | 11 | 7 | 5 | 3 | 1 | 1 | 1 |
| 1-1/2" | 1.986 | 0.794 | 82 | 59 | 37 | 21 | 15 | 9 | 7 | 4 | 1 | 1 | 1 |
| 2" | 3.291 | 1.316 | 135 | 99 | 62 | 36 | 26 | 16 | 11 | 7 | 4 | 3 | 1 |
Areas in square inches, from Chapter 9, Table 4 (2023 NEC). THHN/THWN-2 areas from Table 5.
About ENT
ENT (smurf tube) is the flexible blue tubing used inside walls and slabs, sold in coils rather than sticks. See strap spacing and the fill rules.