EMT (electrical metallic tubing)

3-1/2" EMT conduit fill capacity

3-1/2" EMT has an internal area of 11.545 in². At the 40% limit that applies to more than two conductors, it holds up to 347 12 AWG THHN conductors.

Capacity

Maximum conductors by size and insulation

NEC 2023Every count in this table is transcribed from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Maximum number of same-size, same-insulation conductors in 3-1/2" EMT (11.545 in² internal). Counts above two use the 40% limit; a dash means not even one fits, or the published area table does not list that insulation at that size.
Conductor	THHN / THWN-2	XHHW-2	THW
14 AWG	400	332	220
12 AWG	347	255	177
10 AWG	218	190	138
8 AWG	126	105	83
6 AWG	91	78	63
4 AWG	56	56	47
3 AWG	47	48	40
2 AWG	39	40	34
1 AWG	29	30	24
1/0 AWG	24	25	20
2/0 AWG	20	21	17
3/0 AWG	17	17	14
4/0 AWG	14	14	12
250 kcmil	11	11	10
300 kcmil	10	10	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
1250 kcmil	-	2	1
1500 kcmil	-	1	1
1750 kcmil	-	1	1
2000 kcmil	-	1	1

Fill limits

NEC 2023Every area and limit below is transcribed from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Internal area	11.545 in²
One conductor	53% - 6.1189 in²
Two conductors	31% - 3.5789 in²
More than two	40% - 4.6180 in²

Fitting is not the same as finishing

These counts are the mathematical fill limit, not a promise the pull will go well. A raceway at 39% fill with four 90° bends and a hundred feet between pull points is legal and miserable. Experienced installers routinely size up a trade size on long or bendy runs, and the material cost difference is usually smaller than the labour cost of a fight.

Two other things this table does not model. Nipples 24 inches and shorter between enclosures are permitted a much higher fill. And a mixed set of conductor sizes has to be summed by area rather than looked up by count - the conduit fill calculator handles that.

Remember also that conductor count drives ampacity derating separately. Filling this conduit with current-carrying conductors will reduce what each one can carry - see the bundling adjustment table.

Source: NFPA 70, National Electrical Code, Chapter 9, Table 1; NFPA 70, National Electrical Code, Chapter 9, Table 4; NFPA 70, National Electrical Code, Chapter 9, Table 5. Published by NFPA.NEC 2023Transcribed from the 2023 NEC (NFPA 70, 2023). Confirm against your locally adopted edition and your authority having jurisdiction (AHJ).

Other sizes and types

3" EMT 4" EMT 3-1/2" PVC Sch 40 3-1/2" RMC Conduit fill calculator

Every figure on this page comes from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Reference estimate - verify before you build. AmpSizer reports reference estimates transcribed from published tables in the 2023 NEC (NFPA 70, 2023), and from no other edition. It is not a substitute for the code adopted in your jurisdiction. The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build. Final conductor sizing, overcurrent protection, and installation must be determined by a licensed electrician and approved by your AHJ.

Jurisdictions adopt editions on their own schedule and frequently amend them, so the edition enforced where you work may not be the one cited here. Confirm which edition and which local amendments apply to your job before relying on any value on this page.