6-inch Rigid Metal (RMC) Conduit Fill

Wire capacity of trade size 6 (metric designator 155) Rigid Metal Conduit (RMC), for THHN, XHHW, THW and RHW conductors from 14 AWG to 1000 kcmil.

6-inch Rigid Metal Conduit holds 63 × 1/0 AWG, 36 × 4/0 AWG, 16 × 500 kcmil or 11 × 750 kcmil THHN conductors at 40% fill. Internal area: 29.158 in²; usable at 40%: 11.663 in².

Internal diameter

6.093 in · 154.8 mm

Total area

29.158 in² · 18812 mm²

40% fill (3+ wires)

11.663 in²

31% / 53% (2 / 1 wire)

9.039 / 15.454 in²

Maximum conductors in 6-inch Rigid Metal Conduit
Wire size	THHN	XHHW	THW	RHW	THHN in a nipple (60%)	THHN area (in²)
14 AWG	1202	839	839	398	1803	0.0097
12 AWG	877	644	644	330	1315	0.0133
10 AWG	552	480	480	267	829	0.0211
8 AWG	318	267	267	139	478	0.0366
6 AWG	230	197	160	112	345	0.0507
4 AWG	141	143	120	87	212	0.0824
3 AWG	120	121	103	76	180	0.0973
2 AWG	100	101	87	66	151	0.1158
1 AWG	74	76	61	44	112	0.1562
1/0 AWG	63	64	52	38	94	0.1855
2/0 AWG	52	53	44	33	78	0.2223
3/0 AWG	43	44	37	28	65	0.2679
4/0 AWG	36	36	31	24	54	0.3237
250 kcmil	29	30	25	18	44	0.3970
300 kcmil	25	25	22	16	38	0.4608
350 kcmil	22	22	19	15	33	0.5242
400 kcmil	20	20	17	13	30	0.5863
500 kcmil	16	16	14	11	24	0.7073
600 kcmil	13	13	12	9	20	0.8676
700 kcmil	11	11	10	8	17	0.9887
750 kcmil	11	11	10	8	16	1.0496
800 kcmil	10	10	9	7	15	1.1085
900 kcmil	9	9	8	7	14	1.2311
1000 kcmil	8	8	8	6	13	1.3478

Mixed wire sizes? Calculate it

Conduit type

Trade size

Run length Nipple, 24 in. or shorter (60%)

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6-inch conduit: Rigid Metal Conduit vs other types

Trade size is nominal. The real inside diameter, and so the wire count, changes with the wall thickness of each raceway type.

6-inch trade size across conduit types
Conduit type	ID (in)	Area (in²)	40% (in²)	#12 THHN	#10 THHN	#6 THHN
PVC Schedule 40	6.031	28.567	11.427	859	541	225
PVC Schedule 80	5.709	25.598	10.239	770	485	202
Rigid Metal Conduit	6.093	29.158	11.663	877	552	230

Other Rigid Metal Conduit sizes

Frequently asked questions

How many #12 wires fit in 6-inch Rigid Metal Conduit?

877 conductors of 12 AWG THHN/THWN-2 at the 40% fill limit. With thicker THW or XHHW insulation the count is 644.

What is the inside diameter and area of 6-inch Rigid Metal Conduit?

The internal diameter is 6.093 in. (154.8 mm) and the total cross-sectional area is 29.158 in². The usable area is 11.663 in² at 40% fill, 9.039 in² for two wires and 15.454 in² for one.

What is the largest wire I can pull three of in 6-inch Rigid Metal Conduit?

1000 kcmil THHN: 8 conductors fit at 40% fill. That is three current-carrying conductors with no ground; add the ground’s area and check again with the calculator if you need one.

Can I really load it with that many conductors?

For space, yes. But 877 current-carrying conductors in one raceway means heavy ampacity derating — 10 to 20 conductors are adjusted to 50% of their table ampacity. Fill tells you what fits; derating tells you what it can carry.

NECTables.com is an independent reference and is not affiliated with, endorsed by, or a substitute for the National Fire Protection Association (NFPA). NEC® and National Electrical Code® are registered trademarks of the NFPA. Values shown are commonly published engineering data and independent calculations based on the methods of NFPA 70; they are not a reproduction of the Code. Always confirm against the edition adopted in your jurisdiction, including local amendments, and consult a licensed electrician or engineer before doing electrical work.