Based on the total cross-sectional area of the cables and the allowable fill percentage, calculate the required conduit area:
The National Electric Code (NEC) or local electrical codes specify the maximum percentage of the conduit that can be filled with cables. Commonly, the conduit can be filled to: how to calculate conduit size for cables
Conduit fill is about area , not just diameter. You need each wire’s “area” in square inches. THHN wire dimensions are listed in NEC Chapter 9, Table 5. Based on the total cross-sectional area of the
Required conduit area = 235.62 mm² / 0.4 ≈ 589.05 mm² 4. : Refer to a conduit size chart or table to find the smallest conduit size that meets or exceeds the required conduit area. how to calculate conduit size for cables