✓ NEC 2023 Chapter 9 Table 1 (40% Rule)
Conduit Fill & Wire Sizing Calculator
Calculate minimum EMT/PVC conduit size and verify NEC percentage fill compliance for THHN conductors.
Wire Specifications & Quantity
NEC Conduit Recommendation
Minimum Conduit Size 1/2" EMT Metallic Tubing
Actual Fill % 26.3% ✓ Below 40% limit
Total Conductor Cross Area: 0.0798 sq in
NEC Max Allowable Fill: 40.0% (3+ conductors)
Frequently Asked Questions
What is the maximum conduit fill percentage according to the NEC?
According to NEC Chapter 9, Table 1: For 1 wire, max fill is 53%. For 2 wires, max fill is 31%. For 3 or more conductors, the maximum allowable conduit fill is 40% of the internal cross-sectional area to prevent heat buildup and wire damage during pulling.
How many 12 AWG THHN wires can fit in a 1/2" EMT conduit?
A 1/2" EMT conduit has an internal area of 0.304 sq inches. At the 40% fill limit (0.122 sq in), you can legally pull up to nine (9) #12 AWG THHN conductors (0.0133 sq in each).
How many 10 AWG wires fit in 3/4" conduit?
A 3/4" EMT conduit has an internal area of 0.533 sq inches (40% capacity = 0.213 sq in). You can legally pull up to ten (10) #10 AWG THHN copper wires.