1 Inch Conduit Fill Chart

Q: How many #12 THHN wires fit in 1" conduit?

Up to 26 #12 THHN wires fit in 1" EMT conduit per NEC Chapter 9 Table C1, based on 40% fill for 3+ conductors.

Q: What is the fill area of 1" EMT conduit?

1" EMT conduit has an internal area of 0.346 sq inches. At 40% fill (3+ wires): 0.138 sq inches available. At 31% fill (over 2 wires): 0.107 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 1" conduit? See the complete THHN wire fill chart for 1" EMT, PVC, and rigid conduit per NEC Chapter 9 Table C1. Common uses: 3-6 circuits, sub-panel feeds.

1" Conduit Specifications

1" (1" trade size)

EMT Area

0.346 sq in

PVC Area

0.37 sq in

40% Fill

0.138 sq in

31% Fill

0.107 sq in

Common Use

3-6 circuits

THHN Wire Fill Chart — 1" EMT Conduit

Wire Size	Max Wires (40% fill)
#6 THHN	7 wires
#8 THHN	9 wires
#10 THHN	16 wires
#12 THHN	26 wires
#14 THHN	35 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 1" Conduit

3-6 circuits, sub-panel feeds. This is a common residential size suitable for most branch circuit runs. 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.