NEC Conduit Fill Calculator

THHN/THWN-2 – EMT, IMC, RMC, PVC 40/80
Notes: Uses NEC Ch. 9 Table 1 fill limits (53%/31%/40%). Conduit areas from Table 4; THHN/THWN-2 conductor areas from Table 5 (approx.). Always verify against the edition adopted by your AHJ.

NEC Conduit Fill Calculator

Uses NEC Ch. 9 Table 1 limits and Table 4/5 dimensions (approx.). Always verify with your AHJ/manufacturer.
Conductors in this raceway
Tip: Use “Custom OD” to enter manufacturer jacket OD for exact fill. (We compute area from OD.)
Notes: Fill limits 53% (1 wire) / 31% (2 wires) / 40% (3+ wires). Nipples ≤ 24″ allowed 60%. Jam ratio risk for three equal ODs at ID/OD ≈ 2.8–3.2. Use manufacturer dimensions for final verification with AHJ.