How many wires fit in a conduit? Pick the conduit type and trade size for the full NEC fill chart. Internal areas come from NEC Chapter 9, Table 4, conductor areas from Table 5, and the fill percentages from Table 1 — 53% for one conductor, 31% for two, 40% for three or more.
A 1/2-inch EMT conduit holds 9 12 AWG THHN conductors or 12 14 AWG THHN conductors. A 3/4-inch EMT holds 16 12 AWG. A 1-inch EMT holds 26. Remember that a 12/2 cable pulled as loose conductors is three wires — hot, neutral, and ground — and all three count.
Open the conduit fill calculatorThin-wall steel tubing, the most common raceway in commercial interiors and exposed residential work. Joined with set-screw or compression couplings, …
9 × 12 AWG THHN in 1/2-inch · NEC Article 358
Rigid nonmetallic conduit, solvent-welded. The default for underground runs, wet locations, and corrosive environments. Schedule 80 has thicker walls …
8 × 12 AWG THHN in 1/2-inch · NEC Article 352
Heavy-wall threaded steel conduit — the thickest and strongest raceway in the NEC. Used for service masts, hazardous locations, and anywhere physical …
9 × 12 AWG THHN in 1/2-inch · NEC Article 344
Threaded steel conduit with a thinner wall than RMC, so it is lighter and has slightly more internal area. Permitted anywhere RMC is permitted.…
10 × 12 AWG THHN in 1/2-inch · NEC Article 342
| EMT size | 14 AWG | 12 AWG | 10 AWG | 8 AWG | 6 AWG | 4 AWG | 2 AWG | 1/0 AWG |
|---|---|---|---|---|---|---|---|---|
| 1/2" | 12 | 9 | 5 | 3 | 1 | 1 | 1 | — |
| 3/4" | 22 | 16 | 10 | 6 | 4 | 2 | 1 | 1 |
| 1" | 35 | 26 | 16 | 9 | 7 | 4 | 3 | 1 |
| 1-1/4" | 61 | 45 | 28 | 16 | 12 | 7 | 5 | 3 |
| 1-1/2" | 84 | 61 | 38 | 22 | 16 | 10 | 7 | 4 |
| 2" | 138 | 101 | 63 | 36 | 26 | 16 | 11 | 7 |
| 2-1/2" | 241 | 176 | 111 | 64 | 46 | 28 | 20 | 12 |
| 3" | 364 | 266 | 167 | 96 | 69 | 43 | 30 | 19 |
| 3-1/2" | 476 | 347 | 219 | 126 | 91 | 56 | 40 | 25 |
| 4" | 608 | 443 | 279 | 161 | 116 | 71 | 51 | 32 |
Maximum THHN/THWN-2 conductors, all the same size, at the NEC fill limits. For PVC, rigid metal, or IMC see the type pages above.
| Trade size | EMT (in²) | PVC Sch 40 (in²) | Rigid (RMC) (in²) | IMC (in²) |
|---|---|---|---|---|
| 1/2" | 0.122 | 0.114 | 0.125 | 0.137 |
| 3/4" | 0.213 | 0.203 | 0.220 | 0.235 |
| 1" | 0.346 | 0.333 | 0.355 | 0.384 |
| 1-1/4" | 0.598 | 0.581 | 0.610 | 0.659 |
| 1-1/2" | 0.814 | 0.794 | 0.829 | 0.890 |
| 2" | 1.342 | 1.316 | 1.363 | 1.452 |
| 2-1/2" | 2.343 | 1.878 | 1.946 | 2.054 |
| 3" | 3.538 | 2.907 | 3.000 | 3.169 |
| 3-1/2" | 4.618 | 3.895 | 4.004 | 4.234 |
| 4" | 5.901 | 5.022 | 5.153 | 5.452 |
IMC gives the most usable area up to 2 inches and EMT from 2-1/2 inches up, while PVC Schedule 40 gives the least, because PVC walls are thicker than steel walls of the same trade size. The differences are small but they change the answer at the margin.
A raceway can pass the fill calculation and still be wrong. Three further rules apply to almost every real pull:
NEC Chapter 9, Table 1 allows 53% fill for a single conductor, 31% for exactly two conductors, and 40% for three or more conductors. A conduit nipple 24 inches or shorter between enclosures may be filled to 60%.
Multiply the conduit internal area from NEC Chapter 9, Table 4 by the allowable fill percentage, then divide by the area of one conductor from Table 5. Round down, or up when the decimal is 0.8 or more (Chapter 9, Note 7). For example, 1/2-inch EMT has 0.304 in² internal area; 40% of that is 0.122 in²; divided by the 0.0133 in² area of 12 AWG THHN gives 9 conductors.
In 1/2-inch EMT: 12 conductors of 14 AWG THHN, 9 of 12 AWG, 5 of 10 AWG, or 3 of 8 AWG. PVC Schedule 40 and rigid metal conduit hold slightly different counts because their internal diameters differ.
Yes. Equipment grounding conductors, neutrals, and all circuit conductors count toward the cross-sectional area fill calculation. Grounding conductors are excluded only from the separate count of current-carrying conductors used for ampacity derating under NEC 310.15(C)(1).
Overfilled conduit makes conductors difficult or impossible to pull without damaging insulation, traps heat, and is a code violation that will fail inspection. It also compounds the ampacity derating problem, since more conductors in a raceway means more mutual heating.