Maintain adequate clearance between the conduit wall and the cable. This clearance must accommodate the pulling eye or the cable grip used in the cable pull. In most cases, the minimum cable clearance is 1/2 inch, however, a clearance of 1/4 inch is acceptable if the pull is essentially straight.
Equations for calculating Cable Clearance are listed below. The equation variables are:
C = Cable clearance (inches)
D = Inside diameter of conduit (inches)
dx = 1.05 x largest single cable (inches)