NEC Chapter 9 · Conduit fill
The maximum number of same-size THHN/THWN conductors allowed in 1/2" through 4" EMT, computed straight from the NEC Chapter 9 fill limits.
| Wire (THHN) | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 4" |
|---|---|---|---|---|---|---|---|---|---|
| 14 AWG | 12 | 21 | 35 | 61 | 83 | 138 | 241 | 364 | 608 |
| 12 AWG | 9 | 16 | 25 | 44 | 61 | 100 | 176 | 266 | 443 |
| 10 AWG | 5 | 10 | 16 | 28 | 38 | 63 | 111 | 167 | 279 |
| 8 AWG | 3 | 5 | 9 | 16 | 22 | 36 | 64 | 96 | 161 |
| 6 AWG | 1 | 4 | 6 | 11 | 16 | 26 | 46 | 69 | 116 |
| 4 AWG | 1 | 2 | 4 | 7 | 9 | 16 | 28 | 42 | 71 |
| 3 AWG | 1 | 1 | 3 | 6 | 8 | 13 | 24 | 36 | 60 |
| 2 AWG | 1 | 1 | 2 | 5 | 7 | 11 | 20 | 30 | 50 |
| 1 AWG | 1 | 1 | 1 | 3 | 5 | 8 | 15 | 22 | 37 |
| 1/0 AWG | 0 | 1 | 1 | 3 | 4 | 7 | 12 | 19 | 31 |
| 2/0 AWG | 0 | 1 | 1 | 2 | 3 | 6 | 10 | 15 | 26 |
| 3/0 AWG | 0 | 1 | 1 | 1 | 3 | 5 | 8 | 13 | 22 |
| 4/0 AWG | 0 | 0 | 1 | 1 | 1 | 4 | 7 | 10 | 18 |
Maximum number of same-size THHN/THWN conductors in EMT, computed per NEC Chapter 9 fill limits (one conductor 53%, two 31%, three or more 40%). For mixed sizes, other raceways (RMC, IMC, PVC), or other insulations, use the conduit fill calculator. Verify against the NEC edition adopted locally.
NEC Chapter 9, Table 1 caps how much of a raceway conductors may occupy: 53% for one conductor, 31% for two, and 40% for three or more. This chart applies those limits to same-size THHN/THWN conductors in EMT and shows the maximum count per trade size.
Every conductor counts toward fill — including neutrals and equipment grounding conductors. The percentages come from heat dissipation and the practical ability to pull conductors without scraping insulation, which is why the limit drops as the count rises.
For a mix of conductor sizes, a different raceway (RMC, IMC, PVC Sch 40/80), or other insulations, the conduit fill calculator computes the exact fill. Field PM keeps your raceway schedules and QA/QC records together so the rough-in matches the plan.
It depends on the conduit size and the conductor size and insulation. NEC Chapter 9 limits fill to 53% of the conduit area for one conductor, 31% for two, and 40% for three or more. This chart shows the maximum number of same-size THHN/THWN conductors in EMT.
Sixteen 12 AWG THHN conductors fit in 3/4" EMT at the 40% fill limit. Step down to 1/2" EMT and the limit is nine.
Yes — every conductor in the raceway counts toward fill, including the equipment grounding conductor and the neutral. Count them all when you compare to this chart.
This chart is for conductors that are all the same size. For a mix of sizes (the usual case), add each conductor's area and compare to the conduit's allowable fill — the conduit fill calculator does this for you.
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