Conduit Fill Chart: Maximum THHN/THWN Conductors in EMT, Rigid and PVC by Trade Size, NEC Chapter 9 Tables 1, 4 and 5
Sep 10, 2026
Summary: NEC Chapter 9, Table 1 limits conduit fill to 53 percent of the internal area for one conductor, 31 percent for two, and 40 percent for three or more. The most-used result: 1/2 in EMT holds 12 conductors of 12 AWG THHN or 9 of 10 AWG; 3/4 in EMT holds 16 of 12 AWG or 3 of 6 AWG; 1 in EMT holds 26 of 12 AWG, 7 of 4 AWG or 4 of 2 AWG; 1-1/4 in holds 4 of 1/0; 1-1/2 in holds 4 of 2/0 or 3 of 4/0; 2 in holds 4 of 4/0 or 3 of 350 kcmil. A raceway nipple 24 in or shorter may be filled to 60 percent. The tables below are for THHN/THWN/THWN-2 in EMT from Annex C Table C.1, with rigid and PVC differences noted.
The fill rule
| Number of conductors | Maximum fill, percent of conduit area | Reference |
|---|---|---|
| 1 | 53 | Chapter 9, Table 1 |
| 2 | 31 | Chapter 9, Table 1 |
| 3 or more | 40 | Chapter 9, Table 1 |
| Nipple 24 in or less between boxes or enclosures | 60 | Chapter 9, Note 4; no derating for the nipple |
Equipment grounding conductors count toward fill. Conductors of the same size and insulation use the Annex C tables directly; mixed sizes are calculated from conductor area (Table 5) against conduit area (Table 4).
THHN/THWN in EMT, maximum conductors at 40 percent (Annex C, Table C.1)
| Conductor | 1/2 in | 3/4 in | 1 in | 1-1/4 in | 1-1/2 in | 2 in | 2-1/2 in | 3 in | 4 in |
|---|---|---|---|---|---|---|---|---|---|
| 14 AWG | 12 | 22 | 35 | 61 | 84 | 138 | 241 | 364 | 608 |
| 12 AWG | 9 | 16 | 26 | 45 | 61 | 101 | 176 | 266 | 443 |
| 10 AWG | 5 | 10 | 16 | 28 | 38 | 63 | 111 | 167 | 279 |
| 8 AWG | 3 | 6 | 9 | 16 | 22 | 36 | 64 | 96 | 161 |
| 6 AWG | 2 | 4 | 7 | 12 | 16 | 26 | 46 | 69 | 116 |
| 4 AWG | 1 | 2 | 4 | 7 | 10 | 16 | 28 | 43 | 71 |
| 3 AWG | 1 | 1 | 3 | 6 | 8 | 13 | 24 | 36 | 60 |
| 2 AWG | 1 | 1 | 3 | 5 | 7 | 11 | 20 | 30 | 51 |
| 1 AWG | 0 | 1 | 1 | 4 | 5 | 8 | 15 | 22 | 37 |
| 1/0 AWG | 0 | 1 | 1 | 3 | 4 | 7 | 12 | 19 | 32 |
| 2/0 AWG | 0 | 1 | 1 | 2 | 3 | 6 | 10 | 16 | 26 |
| 3/0 AWG | 0 | 0 | 1 | 1 | 3 | 5 | 8 | 13 | 22 |
| 4/0 AWG | 0 | 0 | 1 | 1 | 2 | 4 | 7 | 11 | 18 |
| 250 kcmil | 0 | 0 | 0 | 1 | 1 | 3 | 6 | 9 | 15 |
| 300 kcmil | 0 | 0 | 0 | 1 | 1 | 3 | 5 | 7 | 13 |
| 350 kcmil | 0 | 0 | 0 | 1 | 1 | 2 | 4 | 6 | 11 |
| 400 kcmil | 0 | 0 | 0 | 0 | 1 | 2 | 4 | 6 | 10 |
| 500 kcmil | 0 | 0 | 0 | 0 | 1 | 1 | 3 | 5 | 8 |
| 600 kcmil | 0 | 0 | 0 | 0 | 0 | 1 | 2 | 4 | 6 |
| 750 kcmil | 0 | 0 | 0 | 0 | 0 | 1 | 2 | 3 | 5 |
Values are the 2023 NEC Annex C Table C.1 for EMT with THHN, THWN, THWN-2. A 0 means the single conductor exceeds 53 percent and is not permitted in that size. Where the table shows 1 or 2, the 53 and 31 percent limits have already been applied.
Rigid metal conduit and PVC
Rigid metal conduit (RMC) has a slightly smaller internal diameter than EMT at each trade size, so RMC counts (Table C.8) are equal or one lower in some cells: 1 in RMC holds 25 of 12 AWG instead of 26; 2 in RMC holds 4 of 4/0, the same as EMT. Schedule 40 PVC (Table C.10) is close to EMT; Schedule 80 PVC (Table C.9) has a thicker wall and holds noticeably fewer: 3/4 in Schedule 80 holds 13 of 12 AWG against 16 in EMT, and 2 in Schedule 80 holds 3 of 4/0 against 4. Use the table for the raceway actually installed.
Calculating mixed sizes
- Look up each conductor's area in Chapter 9, Table 5 (THHN: 12 AWG 0.0133 sq in, 10 AWG 0.0211, 8 AWG 0.0366, 6 AWG 0.0507, 4 AWG 0.0824, 2 AWG 0.1158, 1/0 0.1855, 2/0 0.2223, 3/0 0.2679, 4/0 0.3237, 250 kcmil 0.3970, 350 kcmil 0.5242, 500 kcmil 0.7073).
- Add the areas of all conductors, including the equipment grounding conductor.
- Find the 40 percent column for the raceway in Table 4 (EMT: 1/2 in 0.122 sq in, 3/4 in 0.213, 1 in 0.346, 1-1/4 in 0.598, 1-1/2 in 0.814, 2 in 1.342, 2-1/2 in 2.343, 3 in 3.538, 4 in 5.901).
- Choose the smallest raceway whose 40 percent area is at least the total. Example: three 1/0 THHN plus one 6 AWG ground = 3 x 0.1855 + 0.0507 = 0.607 sq in, which exceeds 1-1/4 in EMT at 0.598, so 1-1/2 in EMT is required.
Fill is not ampacity
Fill tells you what fits. NEC 310.15(C)(1) separately derates ampacity when more than three current-carrying conductors share a raceway longer than 24 in: 4 to 6 conductors at 80 percent, 7 to 9 at 70 percent, 10 to 20 at 50 percent. A 1 in EMT legally full of 26 12 AWG conductors is a 50 percent ampacity run; that is usually the real constraint on branch circuit home runs, not fill.
Quick answers
How many 12 AWG THHN in 3/4 in EMT? 16, at 40 percent fill, per NEC Annex C Table C.1. Ampacity derating applies above three current-carrying conductors.
How many 4/0 in 2 in conduit? 4 in EMT or RMC, 3 in Schedule 80 PVC.
What is the maximum conduit fill percentage? 40 percent for three or more conductors, 31 for two, 53 for one, 60 for a nipple 24 in or shorter.
Does the ground wire count toward fill? Yes. Every conductor in the raceway counts, including the equipment grounding conductor.
Conversions Tech stocks EMT connectors, couplings, conduit bodies, insulated and grounding bushings and straps and hangers in 1/2 through 3 in, UL 514B, by the piece, case and pallet. Fitting selection: compression vs set-screw.
