THHN Conduit Wire Capacity Chart
The maximum number of same-size THHN (or THWN/THWN-2) conductors permitted in each conduit type and trade size, pre-computed to match NEC Annex C so you don’t have to run the fill math. Counts come from the NEC Chapter 9 fill limits (40% for three or more conductors) applied to the standard conduit and wire areas.
EMT — Electrical Metallic Tubing
Thin-wall steel tubing, the workhorse for interior commercial runs. Made in trade sizes 1/2" through 4".
| Trade size | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 12 | 9 | 5 | 3 | 2 | 1 | 1 | 1 | 1 | 1 | — | — | — |
| 3/4" | 22 | 16 | 10 | 6 | 4 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 1" | 35 | 26 | 16 | 9 | 7 | 4 | 3 | 3 | 1 | 1 | 1 | 1 | 1 |
| 1-1/4" | 61 | 45 | 28 | 16 | 12 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 1 |
| 1-1/2" | 84 | 61 | 38 | 22 | 16 | 10 | 8 | 7 | 5 | 4 | 3 | 3 | 2 |
| 2" | 138 | 101 | 63 | 36 | 26 | 16 | 13 | 11 | 8 | 7 | 6 | 5 | 4 |
| 2-1/2" | 241 | 176 | 111 | 64 | 46 | 28 | 24 | 20 | 15 | 12 | 10 | 8 | 7 |
| 3" | 364 | 266 | 167 | 96 | 69 | 43 | 36 | 30 | 22 | 19 | 16 | 13 | 11 |
| 3-1/2" | 476 | 347 | 219 | 126 | 91 | 56 | 47 | 40 | 29 | 25 | 20 | 17 | 14 |
| 4" | 608 | 443 | 279 | 161 | 116 | 71 | 60 | 51 | 37 | 32 | 26 | 22 | 18 |
IMC — Intermediate Metal Conduit
Lighter-wall alternative to rigid with the largest internal area of the steel raceways. Made 1/2" through 4".
| Trade size | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 14 | 10 | 6 | 3 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | — | — |
| 3/4" | 24 | 17 | 11 | 6 | 4 | 3 | 2 | 1 | 1 | 1 | 1 | 1 | 1 |
| 1" | 39 | 29 | 18 | 10 | 7 | 4 | 4 | 3 | 2 | 1 | 1 | 1 | 1 |
| 1-1/4" | 68 | 49 | 31 | 18 | 13 | 8 | 6 | 5 | 4 | 3 | 3 | 2 | 1 |
| 1-1/2" | 91 | 67 | 42 | 24 | 17 | 11 | 9 | 7 | 5 | 4 | 4 | 3 | 2 |
| 2" | 149 | 109 | 69 | 39 | 28 | 17 | 15 | 12 | 9 | 8 | 6 | 5 | 4 |
| 2-1/2" | 211 | 154 | 97 | 56 | 40 | 25 | 21 | 17 | 13 | 11 | 9 | 7 | 6 |
| 3" | 326 | 238 | 150 | 86 | 62 | 38 | 32 | 27 | 20 | 17 | 14 | 12 | 9 |
| 3-1/2" | 436 | 318 | 200 | 115 | 83 | 51 | 43 | 36 | 27 | 23 | 19 | 16 | 13 |
| 4" | 562 | 410 | 258 | 149 | 107 | 66 | 56 | 47 | 35 | 29 | 24 | 20 | 17 |
RMC — Rigid Metal Conduit
Heavy-wall threaded steel for exposed, wet, and mechanical-abuse locations. Made 1/2" through 6".
| Trade size | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 13 | 9 | 6 | 3 | 2 | 1 | 1 | 1 | 1 | 1 | — | — | — |
| 3/4" | 22 | 16 | 10 | 6 | 4 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 1" | 36 | 26 | 17 | 9 | 7 | 4 | 3 | 3 | 1 | 1 | 1 | 1 | 1 |
| 1-1/4" | 63 | 46 | 29 | 16 | 12 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 1 |
| 1-1/2" | 85 | 62 | 39 | 22 | 16 | 10 | 8 | 7 | 5 | 4 | 3 | 3 | 2 |
| 2" | 140 | 102 | 64 | 37 | 27 | 16 | 14 | 11 | 8 | 7 | 6 | 5 | 4 |
| 2-1/2" | 200 | 146 | 92 | 53 | 38 | 23 | 20 | 17 | 12 | 10 | 8 | 7 | 6 |
| 3" | 309 | 225 | 142 | 82 | 59 | 36 | 31 | 26 | 19 | 16 | 13 | 11 | 9 |
| 3-1/2" | 412 | 301 | 189 | 109 | 79 | 48 | 41 | 34 | 25 | 21 | 18 | 15 | 12 |
| 4" | 531 | 387 | 244 | 140 | 101 | 62 | 53 | 44 | 33 | 27 | 23 | 19 | 16 |
| 5" | 833 | 608 | 383 | 221 | 159 | 98 | 83 | 70 | 51 | 43 | 36 | 30 | 25 |
| 6" | 1202 | 877 | 552 | 318 | 230 | 141 | 120 | 100 | 74 | 63 | 52 | 43 | 36 |
PVC Schedule 40
Standard-wall rigid PVC for underground and corrosive locations. Made 1/2" through 6".
| Trade size | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 11 | 8 | 5 | 3 | 1 | 1 | 1 | 1 | 1 | 1 | — | — | — |
| 3/4" | 21 | 15 | 9 | 5 | 4 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 1" | 34 | 25 | 15 | 9 | 6 | 4 | 3 | 3 | 1 | 1 | 1 | 1 | 1 |
| 1-1/4" | 60 | 43 | 27 | 16 | 11 | 7 | 6 | 5 | 3 | 3 | 2 | 1 | 1 |
| 1-1/2" | 82 | 59 | 37 | 21 | 15 | 9 | 8 | 7 | 5 | 4 | 3 | 3 | 2 |
| 2" | 135 | 99 | 62 | 36 | 26 | 16 | 13 | 11 | 8 | 7 | 6 | 5 | 4 |
| 2-1/2" | 193 | 141 | 89 | 51 | 37 | 22 | 19 | 16 | 12 | 10 | 8 | 7 | 6 |
| 3" | 299 | 218 | 137 | 79 | 57 | 35 | 30 | 25 | 18 | 15 | 13 | 11 | 9 |
| 3-1/2" | 401 | 293 | 184 | 106 | 77 | 47 | 40 | 33 | 25 | 21 | 17 | 14 | 12 |
| 4" | 517 | 377 | 238 | 137 | 99 | 61 | 51 | 43 | 32 | 27 | 22 | 18 | 15 |
| 5" | 815 | 594 | 374 | 216 | 156 | 96 | 81 | 68 | 50 | 42 | 35 | 29 | 24 |
| 6" | 1178 | 859 | 541 | 312 | 225 | 138 | 117 | 98 | 73 | 61 | 51 | 42 | 35 |
PVC Schedule 80
Extra-heavy-wall PVC where exposed to damage — the thick wall costs you internal area. Made 1/2" through 6".
| Trade size | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2" | 9 | 6 | 4 | 2 | 1 | 1 | 1 | 1 | — | — | — | — | — |
| 3/4" | 17 | 12 | 7 | 4 | 3 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | — |
| 1" | 28 | 20 | 13 | 7 | 5 | 3 | 3 | 2 | 1 | 1 | 1 | 1 | 1 |
| 1-1/4" | 51 | 37 | 23 | 13 | 9 | 6 | 5 | 4 | 3 | 2 | 1 | 1 | 1 |
| 1-1/2" | 70 | 51 | 32 | 18 | 13 | 8 | 7 | 6 | 4 | 3 | 3 | 2 | 1 |
| 2" | 118 | 86 | 54 | 31 | 22 | 14 | 12 | 10 | 7 | 6 | 5 | 4 | 3 |
| 2-1/2" | 170 | 124 | 78 | 45 | 32 | 20 | 17 | 14 | 10 | 9 | 7 | 6 | 5 |
| 3" | 265 | 193 | 122 | 70 | 51 | 31 | 26 | 22 | 16 | 14 | 11 | 9 | 8 |
| 3-1/2" | 358 | 261 | 164 | 95 | 68 | 42 | 35 | 30 | 22 | 18 | 15 | 13 | 10 |
| 4" | 464 | 338 | 213 | 123 | 89 | 54 | 46 | 39 | 29 | 24 | 20 | 17 | 14 |
| 5" | 736 | 537 | 338 | 195 | 141 | 86 | 73 | 61 | 45 | 38 | 32 | 26 | 22 |
| 6" | 1055 | 770 | 485 | 279 | 202 | 124 | 105 | 88 | 65 | 55 | 46 | 38 | 31 |
Same-size conductors only
These pre-computed counts apply when every conductor in the raceway is the same THHN size — which is the common case for a home run of identical circuits. When you are pulling a mix of sizes, the count does not come from a table: you total each conductor's cross-sectional area and keep the sum at or under 40% of the conduit's internal area (53% for a single conductor, 31% for exactly two). The conduit fill chart gives the usable fill area by trade size, the wire dimensions chart gives each conductor's area, and the conduit fill calculator runs a specific mix for you.
The counts here derive from the same verified data as those tools — conduit internal areas from NEC Chapter 9 Table 4 and THHN areas from Table 5 — and every cell is validated against the published NEC Annex C tables, so the chart and the calculator agree.
Common questions
How many THHN wires fit in a conduit?
It depends on the conduit type and trade size and the wire size. This chart gives the pre-computed maximums straight from NEC Annex C — for example, a 3/4" EMT holds 16 #12 THHN, and a 1" EMT holds 26. The counts assume all conductors are the same THHN size; a mix of sizes has to be figured by area against the 40% fill limit.
How are these counts calculated?
By NEC Chapter 9: the total conductor area may fill at most 40% of the conduit for three or more conductors (53% for one, 31% for exactly two), and NEC Note 7 rounds the result up when the decimal is 0.80 or larger. This chart runs that math from the same conduit areas (Table 4) and THHN wire areas (Table 5) the fill calculator uses, and every value is checked against the published NEC Annex C tables.
Do these numbers apply to THWN too?
Yes. THHN, THWN, and THWN-2 have identical cross-sectional areas, so the conductor counts are the same for all three. The counts are also stable across the 2017, 2020, and 2023 editions of the NEC.
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