3-1/2" IMC conduit fill

3-1/2" Intermediate metal conduit has an inside area of 10.584 sq in (3.671 in across). Three or more wires may take 40 % of it: 4.2336 sq in.

One wire, 53 %: 5.6095 sq in
Two wires, 31 %: 3.2810 sq in
Three or more, 40 %: 4.2336 sq in
Nipple, 60 %: 6.3504 sq in
Support: Every 10 ft, 3 ft from boxes
Sold in: 10 ft sticks

51 #4 THHN, the most it may hold, drawn to scale

How many wires fit in 3-1/2" IMC

All wires the same size and type, by Annex C's method. For a mix of sizes, open the calculator.

Wire size	THHN/THWN-2	XHHW-2	THW/THW-2
14 AWG	436	304	304
12 AWG	318	234	234
10 AWG	200	174	174
8 AWG	115	97	97
6 AWG	83	71	58
4 AWG	51	52	43
3 AWG	43	44	37
2 AWG	36	37	31
1 AWG	27	27	22
1/0 AWG	23	23	19
2/0 AWG	19	19	16
3/0 AWG	16	16	13
4/0 AWG	13	13	11
250 kcmil	10	11	9
300 kcmil	9	9	8
350 kcmil	8	8	7
400 kcmil	7	7	6
500 kcmil	6	6	5
600 kcmil	5	5	4
700 kcmil	4	4	4
750 kcmil	4	4	3
800 kcmil	4	4	3
900 kcmil	3	3	3
1000 kcmil	3	3	3

Smaller: 3" IMC Bigger: 4" IMC

Other 3-1/2" conduit

Conduit	Inside area	#14	#12	#10	#8	#6
Intermediate metal conduit	10.584	436	318	200	115	83
Electrical metallic tubing	11.545	476	347	219	126	91
Rigid metal conduit (RMC, GRC)	10.010	412	301	189	109	79
Rigid PVC conduit, Schedule 40	9.737	401	293	184	106	77
Rigid PVC conduit, Schedule 80	8.688	358	261	164	95	68
Flexible metal conduit (FMC, Greenfield)	9.621	396	289	182	105	76
Liquidtight flexible metal conduit (LFMC)	9.731	401	292	184	106	76

About IMC

IMC has a thinner wall than rigid, so it has a little more room inside size for size. Support follows 342.30: within 3 ft of each box, then every 10 ft, or longer on straight runs with threaded couplings. See strap spacing and the fill rules.