FIG. 01 — REFERENCE TABLE
IMC Conduit Fill Chart
10 supported IMC trade sizes, computed using the site’s transcribed area tables.
Select an insulation and compare the supported IMC sizes below. For mixed conductor sizes, use the conduit fill calculator.
TABLE · IMC × THHN (90°C dry)
NEC 2023 · CH. 9
- 1/2" IMC10 wires40% tier · Note 7 no
- 3/4" IMC17 wires40% tier · Note 7 no
- 1" IMC29 wires40% tier · Note 7 yes
- 1-1/4" IMC49 wires40% tier · Note 7 no
- 1-1/2" IMC67 wires40% tier · Note 7 yes
- 2" IMC109 wires40% tier · Note 7 no
- 2-1/2" IMC154 wires40% tier · Note 7 no
- 3" IMC238 wires40% tier · Note 7 no
- 3-1/2" IMC318 wires40% tier · Note 7 no
- 4" IMC410 wires40% tier · Note 7 yes
| TRADE → WIRE ↓ | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" |
|---|---|---|---|---|---|---|---|---|---|---|
| 14 AWG | 1440% tier · Note 7 no | 2440% tier · Note 7 no | 3940% tier · Note 7 no | 6840% tier · Note 7 yes | 9140% tier · Note 7 no | 14940% tier · Note 7 no | 21140% tier · Note 7 no | 32640% tier · Note 7 no | 43640% tier · Note 7 no | 56240% tier · Note 7 no |
| 12 AWG | 1040% tier · Note 7 no | 1740% tier · Note 7 no | 2940% tier · Note 7 yes | 4940% tier · Note 7 no | 6740% tier · Note 7 yes | 10940% tier · Note 7 no | 15440% tier · Note 7 no | 23840% tier · Note 7 no | 31840% tier · Note 7 no | 41040% tier · Note 7 yes |
| 10 AWG | 640% tier · Note 7 no | 1140% tier · Note 7 no | 1840% tier · Note 7 no | 3140% tier · Note 7 no | 4240% tier · Note 7 no | 6940% tier · Note 7 yes | 9740% tier · Note 7 no | 15040% tier · Note 7 no | 20040% tier · Note 7 no | 25840% tier · Note 7 no |
| 8 AWG | 340% tier · Note 7 no | 640% tier · Note 7 no | 1040% tier · Note 7 no | 1840% tier · Note 7 no | 2440% tier · Note 7 no | 3940% tier · Note 7 no | 5640% tier · Note 7 no | 8640% tier · Note 7 no | 11540% tier · Note 7 no | 14940% tier · Note 7 yes |
| 6 AWG | 231% tier · Note 7 no | 440% tier · Note 7 no | 740% tier · Note 7 no | 1340% tier · Note 7 yes | 1740% tier · Note 7 no | 2840% tier · Note 7 no | 4040% tier · Note 7 no | 6240% tier · Note 7 no | 8340% tier · Note 7 no | 10740% tier · Note 7 no |
| 4 AWG | 153% tier · Note 7 no | 340% tier · Note 7 yes | 440% tier · Note 7 no | 840% tier · Note 7 yes | 1140% tier · Note 7 yes | 1740% tier · Note 7 no | 2540% tier · Note 7 yes | 3840% tier · Note 7 no | 5140% tier · Note 7 no | 6640% tier · Note 7 no |
| 3 AWG | 153% tier · Note 7 no | 231% tier · Note 7 yes | 440% tier · Note 7 yes | 640% tier · Note 7 no | 940% tier · Note 7 no | 1540% tier · Note 7 yes | 2140% tier · Note 7 no | 3240% tier · Note 7 no | 4340% tier · Note 7 no | 5640% tier · Note 7 no |
| 2 AWG | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 no | 540% tier · Note 7 no | 740% tier · Note 7 no | 1240% tier · Note 7 no | 1740% tier · Note 7 no | 2740% tier · Note 7 no | 3640% tier · Note 7 no | 4740% tier · Note 7 no |
| 1 AWG | 153% tier · Note 7 no | 153% tier · Note 7 no | 231% tier · Note 7 yes | 440% tier · Note 7 no | 540% tier · Note 7 no | 940% tier · Note 7 no | 1340% tier · Note 7 no | 2040% tier · Note 7 no | 2740% tier · Note 7 no | 3540% tier · Note 7 yes |
| 1/0 | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 no | 440% tier · Note 7 no | 840% tier · Note 7 yes | 1140% tier · Note 7 no | 1740% tier · Note 7 no | 2340% tier · Note 7 yes | 2940% tier · Note 7 no |
| 2/0 | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 yes | 440% tier · Note 7 no | 640% tier · Note 7 no | 940% tier · Note 7 no | 1440% tier · Note 7 no | 1940% tier · Note 7 no | 2440% tier · Note 7 no |
| 3/0 | — | 153% tier · Note 7 no | 153% tier · Note 7 no | 231% tier · Note 7 yes | 340% tier · Note 7 no | 540% tier · Note 7 no | 740% tier · Note 7 no | 1240% tier · Note 7 yes | 1640% tier · Note 7 yes | 2040% tier · Note 7 no |
| 4/0 | — | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 231% tier · Note 7 no | 440% tier · Note 7 no | 640% tier · Note 7 no | 940% tier · Note 7 no | 1340% tier · Note 7 no | 1740% tier · Note 7 yes |
| 250 | — | — | 153% tier · Note 7 no | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 no | 540% tier · Note 7 no | 840% tier · Note 7 yes | 1040% tier · Note 7 no | 1340% tier · Note 7 no |
| 300 | — | — | 153% tier · Note 7 no | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 no | 440% tier · Note 7 no | 740% tier · Note 7 yes | 940% tier · Note 7 no | 1240% tier · Note 7 yes |
| 350 | — | — | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 231% tier · Note 7 no | 440% tier · Note 7 yes | 640% tier · Note 7 no | 840% tier · Note 7 no | 1040% tier · Note 7 no |
| 400 | — | — | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 231% tier · Note 7 yes | 340% tier · Note 7 no | 540% tier · Note 7 no | 740% tier · Note 7 no | 940% tier · Note 7 no |
| 500 | — | — | — | 153% tier · Note 7 no | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 yes | 440% tier · Note 7 no | 640% tier · Note 7 yes | 740% tier · Note 7 no |
| 600 | — | — | — | 153% tier · Note 7 no | 153% tier · Note 7 no | 153% tier · Note 7 no | 231% tier · Note 7 yes | 340% tier · Note 7 no | 540% tier · Note 7 yes | 640% tier · Note 7 no |
| 700 | — | — | — | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 no | 440% tier · Note 7 no | 540% tier · Note 7 no |
| 750 | — | — | — | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 no | 440% tier · Note 7 no | 540% tier · Note 7 no |
| 800 | — | — | — | — | 153% tier · Note 7 no | 153% tier · Note 7 no | 153% tier · Note 7 no | 340% tier · Note 7 yes | 440% tier · Note 7 yes | 540% tier · Note 7 yes |
| 900 | — | — | — | — | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 231% tier · Note 7 yes | 340% tier · Note 7 no | 440% tier · Note 7 no |
| 1000 | — | — | — | — | 153% tier · Note 7 yes | 153% tier · Note 7 no | 153% tier · Note 7 no | 231% tier · Note 7 yes | 340% tier · Note 7 no | 440% tier · Note 7 no |
IMC — Intermediate Metal Conduit × THHN (90°C dry) · NEC 2023 Ch.9 Tables 4 & 5 · 40% (3+), 31% (2), 53% (1); Note 7 for equal insulated conductor areas
What is Intermediate Metal Conduit?
Intermediate Metal Conduit is the name attached to the IMC area selection in this site's Table 4 dataset. Its 10 supported sizes run from 1/2 through 4 inches.
The IMC/RMC area difference is 0.2220 in² at 2 inches (3.6300 versus 3.4080), or 6.51% relative to RMC. At 4 inches it is 0.7490 in² (13.6310 versus 12.8820), or 5.81%. This dataset has no 5- or 6-inch IMC row, although RMC includes both sizes.
NEC Article 342; Chapter 9 Table 4. These comparisons use this site's stored areas; final-edition cells remain unverified. See the Table 4 guide and source status.
FIG. 02
NOTES & CONTEXT
IMC area comparison
At 1 inch, the stored areas are 0.9590 in² for IMC, 0.8870 for RMC and 0.8640 for EMT. At 4 inches, IMC is 13.6310 in² and EMT is 14.7530 in². IMC does not have a larger area than EMT at every shared size.
Read the count and actual fill
The chart evaluates all three count tiers. A result marked Note 7 can exceed the nominal percentage because the equal-area quotient rounds up at a fractional part of 0.8 or greater. Unsupported insulation/gauge cells show a dash.
See the IMC reference for the definition and area comparison, or data verification status.
FIG. 03
FAQ
How many trade sizes are included for IMC?
10, from 1/2 to 4 inches. The total interior areas at those endpoints are 0.3420 and 13.6310 in².
How many #12 THHN conductors does the engine accept in 1/2-inch IMC?
10 conductors. The total interior area is 0.3420 in². The engine uses the 40% tier; actual fill is 38.89%. Note 7 is not applied.
How many #12 THHN conductors does the engine accept in 3/4-inch IMC?
17 conductors. The total interior area is 0.5860 in². The engine uses the 40% tier; actual fill is 38.58%. Note 7 is not applied.
How many #12 THHN conductors does the engine accept in 1-inch IMC?
29 conductors. The total interior area is 0.9590 in². The engine uses the 40% tier; actual fill is 40.22%. Note 7 is applied.