How this calculator works
For straight pulls the distance is eight times the largest raceway trade size. For angle and U pulls each row is checked separately using six times its largest trade size plus the other entries in that row. The largest row requirement governs the corresponding box dimension. Entry spacing for the same conductors must also meet the six-times rule. Zero in an ungoverned direction means no minimum was calculated for that direction, not permission for a zero-height box.
Formula
Straight dimension >= 8 x largest trade size. Angle/U row opposite-wall distance >= 6 x largest + sum(other sizes in that row). Same-conductor entry separation >= 6 x larger connected raceway trade size.
Worked example
A 2 in straight pull requires 16 in internal length. An angle-pull row with 2 in and 1 in entries requires 6x2+1 = 13 in to the opposite wall; the 16 in straight-pull requirement governs.
Advertisement
Frequently asked questions
Do I use the measured conduit outside diameter?
No. Enter nominal inch trade size. Metric designators are nominal too and are not found by physically converting a measured diameter.
Does the result include box depth?
No. Cover-facing entries, bending space, splice space and listed exceptions need separate review.
Can I treat this as a compliant box selection?
No. Have a qualified electrician check routing, entry spacing, conductor sizes, product listing and the locally adopted edition.