Electrical Wire Sizes for Conduit Fill

Conduit fill calculations depend on the cross-sectional area of each conductor, which includes both the metal conductor and its insulation. Different insulation types (THHN/THWN-2, THWN, XHHW, USE-2) have different thicknesses, resulting in different overall areas for the same wire gauge. This page lists the NEC Chapter 9, Table 5 areas for all supported conductor types and sizes, from 14 AWG through 500 kcmil.

Wire sizes are specified using two systems: AWG (American Wire Gauge) for smaller conductors from 14 AWG through 4/0 AWG, and kcmil (thousand circular mils) for larger conductors starting at 250 kcmil. In the AWG system, smaller numbers indicate larger conductors: 14 AWG is smaller than 12 AWG, which is smaller than 10 AWG. The 4/0 AWG size (sometimes written as "0000") is the largest AWG designation. Beyond that, sizes are specified in kcmil, where larger numbers indicate larger conductors.

Each conductor type below links to a dedicated guide page with minimum conduit size tables, detailed specifications, and application guidance. Click the wire type name to view the full guide, or use the comparison table at the bottom of this page to see how insulation type affects conduit fill.

THHN/THWN-2 Conductors

Wire Size	Area (sq.in.)	Typical Ampacity	Common Application
14 AWG	0.0097	15A	Lighting circuits, small appliance circuits, and general-purpose 15-amp branch circuits. The minimum size permitted for building wiring under NEC Article 210.
12 AWG	0.0133	20A	Standard receptacle circuits, kitchen circuits, bathroom circuits, and general-purpose 20-amp branch circuits. The most commonly installed wire size in residential construction.
10 AWG	0.0211	30A	Electric dryers, window air conditioners, water heaters, and 30-amp dedicated circuits. Also used for long-run 20-amp circuits where voltage drop is a concern.
8 AWG	0.0366	40-50A	Electric ranges, large air conditioning units, hot tubs, and welders. Used for 40-amp and 50-amp branch circuits.
6 AWG	0.0507	55-65A	Subpanels, large motors, EV chargers, and 60-amp feeder circuits. Common for residential subpanel feeders.
4 AWG	0.0824	70-85A	Service entrance conductors for small residential services, large subpanels, and high-amperage feeders.
3 AWG	0.0973	85-100A	100-amp service entrance and feeders. Common for residential main service conductors.
2 AWG	0.1158	95-115A	100-amp to 110-amp services and feeders. Used for residential service entrance conductors.
1 AWG	0.1562	110-130A	Large residential service entrance, commercial feeders, and high-amperage distribution circuits.
1/0 AWG	0.1855	125-150A	150-amp service entrance, large commercial feeders, and residential main service upgrades.
2/0 AWG	0.2223	145-175A	175-amp services, commercial building feeders, and industrial distribution.
3/0 AWG	0.2679	165-200A	200-amp residential main service entrance. The standard size for modern home main services.
4/0 AWG	0.3237	195-230A	200-amp to 225-amp services with adequate headroom. Also used for large commercial feeders.
250 AWG	0.3970	215-255A	Large commercial services, industrial feeders, and high-capacity distribution runs.
300 AWG	0.4608	240-285A	Commercial building main services, industrial distribution, and paralleled feeder runs.
350 AWG	0.5242	260-310A	Large commercial and industrial services. Often used in paralleled configurations.
400 AWG	0.5863	280-335A	Industrial main services, large commercial buildings, and utility interconnections.
500 AWG	0.7073	305-380A	Heavy industrial feeders, large commercial services, and power plant distribution. Typically requires 2-inch or larger conduit.

View complete THHN/THWN-2 conduit fill guide with minimum conduit sizes

THWN Conductors

Wire Size	Area (sq.in.)	Typical Ampacity	Common Application
14 AWG	0.0097	15A	Lighting circuits, small appliance circuits, and general-purpose 15-amp branch circuits. The minimum size permitted for building wiring under NEC Article 210.
12 AWG	0.0133	20A	Standard receptacle circuits, kitchen circuits, bathroom circuits, and general-purpose 20-amp branch circuits. The most commonly installed wire size in residential construction.
10 AWG	0.0211	30A	Electric dryers, window air conditioners, water heaters, and 30-amp dedicated circuits. Also used for long-run 20-amp circuits where voltage drop is a concern.
8 AWG	0.0366	40-50A	Electric ranges, large air conditioning units, hot tubs, and welders. Used for 40-amp and 50-amp branch circuits.
6 AWG	0.0507	55-65A	Subpanels, large motors, EV chargers, and 60-amp feeder circuits. Common for residential subpanel feeders.
4 AWG	0.0824	70-85A	Service entrance conductors for small residential services, large subpanels, and high-amperage feeders.
3 AWG	0.0973	85-100A	100-amp service entrance and feeders. Common for residential main service conductors.
2 AWG	0.1158	95-115A	100-amp to 110-amp services and feeders. Used for residential service entrance conductors.
1 AWG	0.1562	110-130A	Large residential service entrance, commercial feeders, and high-amperage distribution circuits.
1/0 AWG	0.1855	125-150A	150-amp service entrance, large commercial feeders, and residential main service upgrades.
2/0 AWG	0.2223	145-175A	175-amp services, commercial building feeders, and industrial distribution.
3/0 AWG	0.2679	165-200A	200-amp residential main service entrance. The standard size for modern home main services.
4/0 AWG	0.3237	195-230A	200-amp to 225-amp services with adequate headroom. Also used for large commercial feeders.
250 AWG	0.3970	215-255A	Large commercial services, industrial feeders, and high-capacity distribution runs.
300 AWG	0.4608	240-285A	Commercial building main services, industrial distribution, and paralleled feeder runs.
350 AWG	0.5242	260-310A	Large commercial and industrial services. Often used in paralleled configurations.
400 AWG	0.5863	280-335A	Industrial main services, large commercial buildings, and utility interconnections.
500 AWG	0.7073	305-380A	Heavy industrial feeders, large commercial services, and power plant distribution. Typically requires 2-inch or larger conduit.

View complete THWN conduit fill guide with minimum conduit sizes

XHHW Conductors

Wire Size	Area (sq.in.)	Typical Ampacity	Common Application
14 AWG	0.0139	15A	Lighting circuits, small appliance circuits, and general-purpose 15-amp branch circuits. The minimum size permitted for building wiring under NEC Article 210.
12 AWG	0.0181	20A	Standard receptacle circuits, kitchen circuits, bathroom circuits, and general-purpose 20-amp branch circuits. The most commonly installed wire size in residential construction.
10 AWG	0.0243	30A	Electric dryers, window air conditioners, water heaters, and 30-amp dedicated circuits. Also used for long-run 20-amp circuits where voltage drop is a concern.
8 AWG	0.0437	40-50A	Electric ranges, large air conditioning units, hot tubs, and welders. Used for 40-amp and 50-amp branch circuits.
6 AWG	0.0590	55-65A	Subpanels, large motors, EV chargers, and 60-amp feeder circuits. Common for residential subpanel feeders.
4 AWG	0.0814	70-85A	Service entrance conductors for small residential services, large subpanels, and high-amperage feeders.
3 AWG	0.0962	85-100A	100-amp service entrance and feeders. Common for residential main service conductors.
2 AWG	0.1146	95-115A	100-amp to 110-amp services and feeders. Used for residential service entrance conductors.
1 AWG	0.1534	110-130A	Large residential service entrance, commercial feeders, and high-amperage distribution circuits.
1/0 AWG	0.1825	125-150A	150-amp service entrance, large commercial feeders, and residential main service upgrades.
2/0 AWG	0.2190	145-175A	175-amp services, commercial building feeders, and industrial distribution.
3/0 AWG	0.2642	165-200A	200-amp residential main service entrance. The standard size for modern home main services.
4/0 AWG	0.3197	195-230A	200-amp to 225-amp services with adequate headroom. Also used for large commercial feeders.
250 AWG	0.3904	215-255A	Large commercial services, industrial feeders, and high-capacity distribution runs.
300 AWG	0.4536	240-285A	Commercial building main services, industrial distribution, and paralleled feeder runs.
350 AWG	0.5166	260-310A	Large commercial and industrial services. Often used in paralleled configurations.
400 AWG	0.5782	280-335A	Industrial main services, large commercial buildings, and utility interconnections.
500 AWG	0.6984	305-380A	Heavy industrial feeders, large commercial services, and power plant distribution. Typically requires 2-inch or larger conduit.

View complete XHHW conduit fill guide with minimum conduit sizes

USE-2 Conductors

Wire Size	Area (sq.in.)	Typical Ampacity	Common Application
14 AWG	0.0139	15A	Lighting circuits, small appliance circuits, and general-purpose 15-amp branch circuits. The minimum size permitted for building wiring under NEC Article 210.
12 AWG	0.0181	20A	Standard receptacle circuits, kitchen circuits, bathroom circuits, and general-purpose 20-amp branch circuits. The most commonly installed wire size in residential construction.
10 AWG	0.0243	30A	Electric dryers, window air conditioners, water heaters, and 30-amp dedicated circuits. Also used for long-run 20-amp circuits where voltage drop is a concern.
8 AWG	0.0437	40-50A	Electric ranges, large air conditioning units, hot tubs, and welders. Used for 40-amp and 50-amp branch circuits.
6 AWG	0.0590	55-65A	Subpanels, large motors, EV chargers, and 60-amp feeder circuits. Common for residential subpanel feeders.
4 AWG	0.0814	70-85A	Service entrance conductors for small residential services, large subpanels, and high-amperage feeders.
3 AWG	0.0962	85-100A	100-amp service entrance and feeders. Common for residential main service conductors.
2 AWG	0.1146	95-115A	100-amp to 110-amp services and feeders. Used for residential service entrance conductors.
1 AWG	0.1534	110-130A	Large residential service entrance, commercial feeders, and high-amperage distribution circuits.
1/0 AWG	0.1825	125-150A	150-amp service entrance, large commercial feeders, and residential main service upgrades.
2/0 AWG	0.2190	145-175A	175-amp services, commercial building feeders, and industrial distribution.
3/0 AWG	0.2642	165-200A	200-amp residential main service entrance. The standard size for modern home main services.
4/0 AWG	0.3197	195-230A	200-amp to 225-amp services with adequate headroom. Also used for large commercial feeders.
250 AWG	0.3904	215-255A	Large commercial services, industrial feeders, and high-capacity distribution runs.
300 AWG	0.4536	240-285A	Commercial building main services, industrial distribution, and paralleled feeder runs.
350 AWG	0.5166	260-310A	Large commercial and industrial services. Often used in paralleled configurations.
400 AWG	0.5782	280-335A	Industrial main services, large commercial buildings, and utility interconnections.
500 AWG	0.6984	305-380A	Heavy industrial feeders, large commercial services, and power plant distribution. Typically requires 2-inch or larger conduit.

View complete USE-2 conduit fill guide with minimum conduit sizes

Wire Size Comparison Across Insulation Types

The table below shows how cross-sectional area varies by insulation type for each wire gauge. THHN/THWN-2 conductors are generally the smallest due to their thin nylon-jacketed PVC insulation, while XHHW and USE-2 are larger due to their thicker cross-linked polyethylene insulation. Choosing THHN/THWN-2 when permitted maximizes the number of conductors that fit in a given conduit size.

Wire Size	THHN/THWN-2 (sq.in.)	THWN (sq.in.)	XHHW (sq.in.)	USE-2 (sq.in.)
14 AWG	0.0097	0.0097	0.0139	0.0139
12 AWG	0.0133	0.0133	0.0181	0.0181
10 AWG	0.0211	0.0211	0.0243	0.0243
8 AWG	0.0366	0.0366	0.0437	0.0437
6 AWG	0.0507	0.0507	0.0590	0.0590
4 AWG	0.0824	0.0824	0.0814	0.0814
3 AWG	0.0973	0.0973	0.0962	0.0962
2 AWG	0.1158	0.1158	0.1146	0.1146
1 AWG	0.1562	0.1562	0.1534	0.1534
1/0 AWG	0.1855	0.1855	0.1825	0.1825
2/0 AWG	0.2223	0.2223	0.2190	0.2190
3/0 AWG	0.2679	0.2679	0.2642	0.2642
4/0 AWG	0.3237	0.3237	0.3197	0.3197
250 AWG	0.3970	0.3970	0.3904	0.3904
300 AWG	0.4608	0.4608	0.4536	0.4536
350 AWG	0.5242	0.5242	0.5166	0.5166
400 AWG	0.5863	0.5863	0.5782	0.5782
500 AWG	0.7073	0.7073	0.6984	0.6984