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Conduit Fill Calculator
NEC Chapter 9. Checks the 40% fill limit for 3 or more conductors in a raceway.
Conduit Fill (NEC Ch. 9)
Wires
NEC conduit fill limits
- 1 conductor: 53% fill allowed
- 2 conductors: 31% fill allowed
- 3+ conductors: 40% fill allowed (most common)
This calculator uses the 40% rule for 3+ conductors per NEC Chapter 9, Table 1.
Wire cross-sectional areas (NEC Annex C)
- 14 AWG0.0097 in²
- 12 AWG0.0133 in²
- 10 AWG0.0211 in²
- 8 AWG0.0366 in²
- 6 AWG0.0507 in²
- 4 AWG0.0824 in²
THHN/THWN-2 insulation. Values from NEC Table 5.
Common conduit sizes
- ½" conduit0.196 in²
- ¾" conduit0.384 in²
- 1" conduit0.660 in²
- 1¼" conduit1.084 in²
- 1½" conduit1.502 in²
- 2" conduit2.642 in²
EMT trade sizes. Internal area from NEC Chapter 9, Table 4.
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