Maximum THHN/THWN-2 wires in EMT
These are the most same-size conductors allowed under NEC Chapter 9, Table 1 (40% fill for three or more wires), using the Table 4 conduit areas and Table 5 wire areas, with the Note 7 rule that rounds up when the result has a decimal of 0.8 or more. Count equipment grounding wires too.
| Conduit | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 12 | 9 | 5 | 3 | 1 | 1 | 1 | 1 | 1 | 0 | 0 |
| 3/4" | 22 | 16 | 10 | 6 | 4 | 2 | 1 | 1 | 1 | 1 | 1 |
| 1" | 35 | 26 | 16 | 9 | 7 | 4 | 3 | 3 | 1 | 1 | 1 |
| 1-1/4" | 61 | 45 | 28 | 16 | 12 | 7 | 6 | 5 | 4 | 3 | 2 |
| 1-1/2" | 84 | 61 | 38 | 22 | 16 | 10 | 8 | 7 | 5 | 4 | 3 |
| 2" | 138 | 101 | 63 | 36 | 26 | 16 | 13 | 11 | 8 | 7 | 6 |
Maximum THHN/THWN-2 wires in PVC Schedule 40
Schedule 40 PVC has thicker walls than EMT, so the inside is a little smaller and the counts are the same or lower.
| Conduit | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 11 | 8 | 5 | 3 | 1 | 1 | 1 | 1 | 0 | 0 | 0 |
| 3/4" | 21 | 15 | 9 | 5 | 4 | 1 | 1 | 1 | 1 | 1 | 1 |
| 1" | 34 | 25 | 15 | 9 | 6 | 4 | 3 | 3 | 1 | 1 | 1 |
| 1-1/4" | 60 | 43 | 27 | 16 | 11 | 7 | 6 | 5 | 3 | 3 | 2 |
| 1-1/2" | 82 | 59 | 37 | 21 | 15 | 9 | 8 | 7 | 5 | 4 | 3 |
| 2" | 135 | 99 | 62 | 36 | 26 | 16 | 13 | 11 | 8 | 7 | 6 |
What size conduit for a given number of wires?
Smallest EMT trade size that holds that many same-size THHN conductors:
| Wires | 14 AWG | 12 AWG | 10 AWG | 8 AWG | 6 AWG |
|---|---|---|---|---|---|
| 2 | 1/2" | 1/2" | 1/2" | 1/2" | 3/4" |
| 3 | 1/2" | 1/2" | 1/2" | 1/2" | 3/4" |
| 4 | 1/2" | 1/2" | 1/2" | 3/4" | 3/4" |
| 5 | 1/2" | 1/2" | 1/2" | 3/4" | 1" |
| 6 | 1/2" | 1/2" | 3/4" | 3/4" | 1" |
| 7 | 1/2" | 1/2" | 3/4" | 1" | 1" |
| 8 | 1/2" | 1/2" | 3/4" | 1" | 1-1/4" |
| 9 | 1/2" | 1/2" | 3/4" | 1" | 1-1/4" |
| 10 | 1/2" | 3/4" | 3/4" | 1-1/4" | 1-1/4" |
| 11 | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/4" |
| 12 | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/4" |
Example: a 120 V circuit with a hot, neutral and ground is three conductors, which fit in 1/2 inch EMT even at 12 AWG. Six 12 AWG wires (two circuits with shared ground) also fit in 1/2 inch, and ten need 3/4 inch.
How the fill is calculated
Fill % = (number of wires × wire area) ÷ conduit internal area × 100
The limit is 53% for one wire, 31% for two and 40% for three or more. THHN wire areas used: 14 AWG 0.0097 in², 12 AWG 0.0133, 10 AWG 0.0211, 8 AWG 0.0366, 6 AWG 0.0507, 4 AWG 0.0824, 3 AWG 0.0973, 2 AWG 0.1158, 1 AWG 0.1562, 1/0 0.1855, 2/0 0.2223. Mixed sizes must be added up wire by wire with the calculator.
Frequently asked questions
How many 12 gauge wires fit in 1/2 inch conduit?
Nine THHN conductors in 1/2 inch EMT, or eight in 1/2 inch Schedule 40 PVC.
How many 10 gauge wires fit in 3/4 inch conduit?
Ten THHN conductors in 3/4 inch EMT. Check the table for PVC, which holds slightly fewer.
Does the ground wire count?
Yes. Equipment grounding conductors count for fill, but not for current-carrying derating.
What is the NEC fill limit?
53% for one conductor, 31% for two and 40% for three or more, from Chapter 9, Table 1.