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 Conduit / Raceway
Tip: Use “Custom OD” to enter manufacturer jacket OD for exact fill. (Otherwise use THHN - Or - XHHW And we'll compute for you.)
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.
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