Electrical

Conduit Internal Area by Type and Trade Size

Internal cross-sectional area of EMT, ENT, FMC, IMC, LFMC, LFNC-B, RMC, and Schedule 40 and 80 PVC by trade size, the figure conduit fill is measured against.

Read before using this table

Reference tables here are reproduced for convenience and may not match the edition of the code or standard adopted in your jurisdiction. They are not a substitute for the published document. Verify every value against the current adopted edition and the manufacturer data for the specific product before using it in a design, an installation, or an inspection.

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Source of these values

Internal diameters as commonly published for NFPA 70 Chapter 9 Table 4. Areas are computed as pi/4 times the diameter squared, which is how the table itself is derived, and every value is checked at build time against a separately recorded copy of the published area. Fill percentages are from Chapter 9 Table 1. Verify against your adopted edition.

Trade size	EMT, sq in	ENT, sq in	FMC, sq in	IMC, sq in	LFMC, sq in	LFNC-B, sq in	RMC, sq in	PVC Sch 80, sq in	PVC Sch 40, sq in
3/8 in	—	—	0.116	—	0.192	0.192	—	—	—
1/2 in	0.304	0.246	0.317	0.342	0.314	0.314	0.314	0.217	0.285
3/4 in	0.533	0.454	0.533	0.586	0.541	0.541	0.549	0.409	0.508
1 in	0.864	0.785	0.817	0.959	0.873	0.873	0.887	0.688	0.832
1-1/4 in	1.496	1.410	1.277	1.647	1.528	1.528	1.526	1.237	1.453
1-1/2 in	2.036	1.936	1.858	2.225	1.981	1.981	2.071	1.711	1.986
2 in	3.356	3.205	3.269	3.631	3.246	3.246	3.408	2.874	3.291
2-1/2 in	5.858	—	4.909	5.135	4.881	—	4.866	4.119	4.695
3 in	8.846	—	7.069	7.922	7.475	—	7.499	6.442	7.268
3-1/2 in	11.545	—	9.621	10.584	9.731	—	10.010	8.688	9.737
4 in	14.753	—	12.566	13.631	12.692	—	12.882	11.258	12.554
5 in	—	—	—	—	—	—	20.212	17.855	19.761
6 in	—	—	—	—	—	—	29.158	25.598	28.567

In short

Conduit fill is measured against the raceway internal area from NFPA 70 Chapter 9 Table 4, and that area differs by conduit type at the same trade size. Half-inch EMT has 0.304 square inches, half-inch RMC 0.314, half-inch IMC 0.342, and half-inch Schedule 80 PVC only 0.217. The usable share is 53% for one conductor, 31% for two, and 40% for three or more.

Notes and limits

Values are the 100% internal area. Multiply by 0.53, 0.31, or 0.40 for the usable area with one, two, or three or more conductors, or use the conduit fill calculator, which does this and reports the smallest size that fits.
A dash means the raceway is not made in that trade size under its article.
A nipple not over 24 inches long is permitted 60% fill under Chapter 9 Note 4.
Every conductor counts toward fill, including equipment grounding conductors, even though grounding conductors do not count toward the ampacity adjustment factor.
EMT, ENT, FMC, IMC, LFMC, LFNC-B, RMC and PVC are governed by Articles 358, 362, 348, 342, 350, 356, 344 and 352 respectively.

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