NEC Chapter 9
Conduit Fill Chart (THHN in EMT)
Maximum number of THHN conductors per EMT trade size at the NEC 40% fill limit for three or more conductors. Read down your wire size, across to your conduit size.
THHN / THWN-2 Conductors in EMT at 40% Fill
| Wire (AWG/kcmil) | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" |
|---|---|---|---|---|---|---|---|---|---|---|
| 14 | 12 | 22 | 35 | 61 | 84 | 138 | 241 | 364 | 476 | 608 |
| 12 | 9 | 16 | 26 | 45 | 61 | 101 | 176 | 266 | 347 | 443 |
| 10 | 5 | 10 | 16 | 28 | 38 | 63 | 111 | 167 | 219 | 279 |
| 8 | 3 | 6 | 9 | 16 | 22 | 36 | 64 | 96 | 126 | 161 |
| 6 | 2 | 4 | 7 | 12 | 16 | 26 | 46 | 69 | 91 | 116 |
| 4 | 1 | 2 | 4 | 7 | 10 | 16 | 28 | 43 | 56 | 71 |
| 3 | 1 | 2 | 3 | 6 | 8 | 13 | 24 | 36 | 47 | 60 |
| 2 | 1 | 2 | 3 | 5 | 7 | 11 | 20 | 30 | 40 | 51 |
| 1 | 0 | 1 | 2 | 4 | 5 | 8 | 15 | 22 | 29 | 37 |
| 1/0 | 0 | 1 | 2 | 3 | 4 | 7 | 12 | 19 | 25 | 32 |
| 2/0 | 0 | 1 | 1 | 2 | 3 | 6 | 10 | 16 | 20 | 26 |
| 3/0 | 0 | 0 | 1 | 2 | 3 | 5 | 8 | 13 | 17 | 22 |
| 4/0 | 0 | 0 | 1 | 2 | 2 | 4 | 7 | 11 | 14 | 18 |
| 250 | 0 | 0 | 1 | 1 | 2 | 3 | 6 | 9 | 11 | 15 |
| 350 | 0 | 0 | 0 | 1 | 1 | 2 | 4 | 6 | 9 | 11 |
| 500 | 0 | 0 | 0 | 1 | 1 | 2 | 3 | 5 | 6 | 8 |
THHN and THWN-2 share the same area, so counts are identical. For a single conductor use 53% fill, for exactly two use 31%, and for a nipple 24 inches or shorter use 60% (NEC Chapter 9, Table 1). For IMC, RMC, or PVC, or mixed wire sizes, use the conduit fill calculator.
How the Count Is Calculated
Conduit fill is an area comparison. Max conductors = (conduit internal area × fill limit) / conductor area, rounded down. The conduit internal area comes from NEC Chapter 9, Table 4, the fill limit is 40% for three or more conductors from Table 1, and the conductor area comes from Table 5. For 3/4 inch EMT that is 0.533 sq in × 0.40 = 0.213 sq in of usable space, and each #12 THHN is 0.0133 sq in, so 0.213 / 0.0133 = 16.03, which gives 16 conductors. One rounding wrinkle from NEC Chapter 9, Note 7: you round up only when the decimal is 0.8 or larger, otherwise you round down. That is why #12 THHN in 1 inch EMT works out to 26 (25.98 rounds up) but in 3/4 inch EMT it is 16 (16.03 rounds down).
Every conductor in the raceway counts, including the equipment grounding conductor. The fill limit is about heat dissipation and pulling tension, not just physical space, which is why the limit is 40% rather than 100%.
Frequently Asked Questions
How many 12 AWG THHN wires fit in 3/4 inch EMT?
16 #12 THHN conductors fit in 3/4 inch EMT at the NEC 40% fill limit. The 3/4 inch EMT internal area is 0.533 sq in, so 0.533 x 0.40 = 0.213 sq in allowable, divided by 0.0133 sq in per #12 THHN = 16.
How many 12 AWG THHN wires fit in 1/2 inch EMT?
9 #12 THHN conductors fit in 1/2 inch EMT at 40% fill. The 1/2 inch EMT area is 0.304 sq in, so 0.304 x 0.40 = 0.122 sq in, divided by 0.0133 = 9.
How many 10 AWG THHN wires fit in 1/2 inch EMT?
5 #10 THHN conductors fit in 1/2 inch EMT at 40% fill (0.304 x 0.40 = 0.122 sq in, divided by 0.0211 sq in per #10 THHN = 5).
What is the fill limit for conduit?
The NEC Chapter 9, Table 1 fill limit is 40% for three or more conductors, 31% for exactly two, 53% for a single conductor, and 60% for a nipple 24 inches or shorter. This chart uses the 40% limit, which covers almost all installations.
Do ground wires count in conduit fill?
Yes. Every conductor in the raceway counts toward conduit fill, including the equipment grounding conductor, based on its own cross-sectional area from NEC Chapter 9, Table 5. Only bare grounds use the bare-conductor area; insulated grounds use the insulated area.
Is this chart the same for THWN-2 wire?
Yes. THHN and THWN-2 have identical cross-sectional areas in NEC Chapter 9, Table 5, so the conductor counts are the same. XHHW, RHH, RHW, TW, and THW are larger, so fewer fit. Use the conduit fill calculator for those insulations.
Related Calculators & Charts
Conduit Fill Calculator
Any mix of wire sizes and insulations in EMT, IMC, RMC, PVC, or ENT, with exact fill percentage and pass/fail.
Wire Ampacity Chart (310.16)
Once the wires fit, confirm they carry the load with the copper and aluminum ampacity table.
Box Fill Volume Chart (314.16)
The junction-box version: cubic inches per conductor with device, clamp, and ground rules.
Different conduit or a mix of wires?
This chart is THHN in EMT at 40%. For IMC, RMC, PVC, ENT, single or two-conductor limits, or any mix of sizes, the conduit fill calculator runs the exact NEC Chapter 9 math.