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Conduit Fill Calculator

Check raceway fill percent against NEC Chapter 9 limits.

Inputs

Conductors and raceway

Copper THHN. Cross-sectional areas come from NEC Chapter 9 Table 5. Other insulation types have different areas.

Count every conductor, including the equipment grounding conductor.

Electrical metallic tubing, using internal areas from NEC Chapter 9 Table 4. PVC and other raceway types differ.

NEC Chapter 9 Table 1 allows 60% fill for nipples 24 in or less, and Table 1 Note 4 permits a single conductor at 53%.

Result

Allowed fill for this raceway
40.0 %
Raceway fill
7.5 %
Within the fill limit (1 = yes)
1
Total conductor area
0.0399 sq in
Most conductors of this size
16
Spare cross-sectional area
0.1733 sq in

What to check

  • NEC Table 5 wire areas
  • NEC Table 4 conduit areas

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Screening tool. Verify against the NEC as adopted locally, the AHJ, nameplate data, and metered conditions before acting.

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