The below tool will assist to perform NEC conduit fill calculation.
How is conduit fill calculated ?
Conduit fill and sizing should be complied with Table 1 of NEC Chapter 9.
Total Cable Area / Total Conduit Area < Allowable Percent Fill
Total Cable Area
∑ (Cable Overall Diameter^2 / 4 * 3.14)
Total Conduit Area
As NEC 2017 Chapter 9 – Table 4
Allowable Percent Fill
– 53% for 1 no. of cable – 31% for 2 nos. of cable – 40% for over 2 nos. of cable
Conduit fill calculation result is based on normal conditions of good practice cable routing and alignment of conductors. For example, the total number of bends between 2 pull points can not exceed 360o or the maximum number of conductors in a connection box.
RMC conduit size, internal diameter and internal total area of is as below:
For other type of conduit (i.e. ENT or PVC-80), refer to chapter 9 – Table 4.