Cross Section

EMT (Electrical Metallic Tubing)

Thin-wall Steel Conduit

Lightweight steel conduit with thin walls. Most common for commercial and industrial exposed work. Cannot be threaded; uses set-screw or compression fittings. NEC Article 358.

Material

Steel (zinc-coated)

Sizes

6 trade sizes

Dimensions & Fill Capacities

NEC Chapter 9

Trade Size	OD (in)	ID (in)	Total Area (in2)	40% Fill (in2)	#14 AWG	#12 AWG	#10 AWG
1/2"	0.706	0.622	0.304	0.122	8	6	4
3/4"	0.922	0.824	0.533	0.213	14	10	7
1"	1.163	1.049	0.864	0.346	22	16	11
1-1/4"	1.510	1.380	1.496	0.598	38	28	19
1-1/2"	1.750	1.610	2.036	0.814	52	38	26
2"	2.197	2.067	3.356	1.342	85	62	43

NEC Fill Rules

• 40% fill: Maximum for 3 or more conductors (NEC Table 1)
• 53% fill: Allowable for 2 conductors only
• 60% fill: Nipple (conduit ≤24 inches) special rule
• Derating: Current-carrying conductors >3 require ampacity adjustment (NEC 310.15)

Cross Section

Rigid Metal Conduit (RMC)

Heavy-wall Threaded Steel

Heavy-duty threaded steel conduit for severe environments. Used in industrial, hazardous locations, and outdoor applications. NEC Article 344. Can be bent with proper tools.

Material

Steel (hot-dip galvanized)

Sizes

6 trade sizes

Dimensions & Fill Capacities

NEC Chapter 9

Trade Size	OD (in)	ID (in)	Total Area (in2)	40% Fill (in2)	#14 AWG	#12 AWG	#10 AWG
1/2"	0.840	0.622	0.304	0.122	8	6	4
3/4"	1.050	0.824	0.533	0.213	14	10	7
1"	1.315	1.049	0.864	0.346	22	16	11
1-1/4"	1.660	1.380	1.496	0.598	38	28	19
1-1/2"	1.900	1.610	2.036	0.814	52	38	26
2"	2.375	2.067	3.356	1.342	85	62	43

NEC Fill Rules

• Threaded: Requires threading machine or pre-threaded sections
• Bending: Minimum bend radius = 6×¹onduit diameter (NEC 344.24)
• Supports: Every 10 ft and within 3 ft of boxes (NEC 344.30)
• Corrosion: Hot-dip galvanized for outdoor; stainless for severe

Cross Section

PVC Conduit (Schedule 40)

Plastic Non-metallic

Corrosion-resistant plastic conduit for underground, wet, and corrosive locations. Cannot be used where subject to physical damage. NEC Article 352. Uses solvent-weld fittings.

Material

PVC (polyvinyl chloride)

Sizes

6 trade sizes

Dimensions & Fill Capacities

NEC Chapter 9

Trade Size	OD (in)	ID (in)	Total Area (in2)	40% Fill (in2)	#14 AWG	#12 AWG	#10 AWG
1/2"	0.840	0.602	0.285	0.114	7	5	3
3/4"	1.050	0.804	0.508	0.203	13	9	6
1"	1.315	1.033	0.835	0.334	21	15	10
1-1/4"	1.660	1.360	1.453	0.581	37	27	18
1-1/2"	1.900	1.590	1.986	0.794	50	37	25
2"	2.375	2.047	3.294	1.318	83	61	42

NEC Fill Rules

• Underground: Minimum 18" cover for residential (NEC 300.5)
• Expansion: Requires expansion fittings for temperature changes
• Support: Every 3 ft for sizes ≤1", every 5 ft for larger (NEC 352.30)
• Sunlight: Must be marked "Sunlight Resistant" for outdoor use

Cross Section

Flexible Metal Conduit (FMC)

Greenfield / Flex

Spiral-wound flexible metal conduit for vibrations, tight spaces, and equipment connections. Limited to 6 ft for grounding path. NEC Article 348. Liquid-tight version (LFMC) for wet areas.

Material

Galvanized steel strip

Sizes

6 trade sizes

Dimensions & Fill Capacities

NEC Chapter 9

Trade Size	OD (in)	ID (in)	Total Area (in2)	40% Fill (in2)	#14 AWG	#12 AWG	#10 AWG
1/2"	0.800	0.546	0.234	0.094	6	4	2
3/4"	0.980	0.710	0.396	0.158	10	7	5
1"	1.200	0.920	0.665	0.266	17	12	8
1-1/4"	1.480	1.150	1.039	0.416	26	19	13
1-1/2"	1.680	1.350	1.431	0.572	36	26	18
2"	2.100	1.770	2.461	0.984	62	45	31

NEC Fill Rules

• Grounding: Limited to 6 ft for equipment grounding path (NEC 250.118)
• Applications: Motors, transformers, vibration isolation
• LFMC: Liquid-tight version required for wet locations
• Bends: No minimum radius but avoid kinking during installation