PVC Schedule 40

4" PVC Sch 40 conduit fill capacity

4" PVC Sch 40 has an internal area of 12.554 in². At the 40% limit that applies to more than two conductors, it holds up to 377 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 4" PVC Sch 40 (12.554 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	361	240
12 AWG	377	277	193
10 AWG	237	206	150
8 AWG	137	114	90
6 AWG	99	85	69
4 AWG	60	61	51
3 AWG	51	52	44
2 AWG	43	43	37
1 AWG	32	32	26
1/0 AWG	27	27	22
2/0 AWG	22	22	19
3/0 AWG	18	19	16
4/0 AWG	15	15	13
250 kcmil	12	12	10
300 kcmil	10	11	9
350 kcmil	9	9	8
400 kcmil	8	8	7
500 kcmil	7	7	6
600 kcmil	5	5	5
700 kcmil	5	5	4
750 kcmil	4	4	4
800 kcmil	4	4	4
900 kcmil	4	4	3
1000 kcmil	3	3	3
1250 kcmil	-	2	2
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	12.554 in²
One conductor	53% - 6.6536 in²
Two conductors	31% - 3.8917 in²
More than two	40% - 5.0216 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

3-1/2" PVC Sch 40 4" EMT 4" 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.