4 Inch Conduit Fill Chart

Q: How many #12 THHN wires fit in 4" conduit?

Up to undefined #12 THHN wires fit in 4" EMT conduit per NEC Chapter 9 Table C1, based on 40% fill for 3+ conductors.

Q: What is the fill area of 4" EMT conduit?

4" EMT conduit has an internal area of 3.694 sq inches. At 40% fill (3+ wires): 1.478 sq inches available. At 31% fill (over 2 wires): 1.145 sq inches.

Q: What are the NEC conduit fill rules?

1 wire: 53% fill. 2 wires: 31% fill. 3+ wires: 40% fill per NEC Chapter 9 Table 1. These percentages apply to the conduit internal cross-sectional area.

How many wires fit in 4" conduit? See the complete THHN wire fill chart for 4" EMT, PVC, and rigid conduit per NEC Chapter 9 Table C1. Common uses: Large industrial feeders, service mains.

4" Conduit Specifications

4" (4" trade size)

EMT Area

3.694 sq in

PVC Area

3.85 sq in

40% Fill

1.478 sq in

31% Fill

1.145 sq in

Common Use

Large industrial feeders

THHN Wire Fill Chart — 4" EMT Conduit

Wire Size	Max Wires (40% fill)
#2 THHN	35 wires
#4 THHN	49 wires
#6 THHN	70 wires
#1/0 THHN	24 wires
#2/0 THHN	21 wires
#3/0 THHN	18 wires
#4/0 THHN	15 wires

Based on NEC Chapter 9 Table C1 for EMT conduit with THHN/THWN-2 conductors at 40% fill (3+ conductors).

NEC Conduit Fill Rules

1 conductor: 53% of conduit area. 2 conductors: 31% of conduit area. 3+ conductors: 40% of conduit area. These rules are per NEC Chapter 9 Table 1 and apply to all conduit types (EMT, PVC, rigid).

Equipment grounding conductors count toward fill but not toward ampacity derating. Bare grounds use less area than insulated conductors of the same gauge.

When to Use 4" Conduit

Large industrial feeders, service mains. This is a commercial/industrial size for large feeders and service entrance conductors. Use our Conduit Fill Calculator for exact fill calculations with mixed wire sizes.

Disclaimer: Based on NEC Chapter 9 tables. Verify with local codes. Consult a licensed electrician.