By Zencalcy Editorial TeamLast reviewed About us
A pull box must be large enough for the conductors to be pulled without damage. The NEC rule is simple to apply: eight times the largest conduit trade size for a straight pull, and six times plus the distance between entries for an angle pull.
Pull-box dimensions for conduit, per NEC 314.28.
Straight: length = 8 × trade size Angle: length = 6 × trade size + distance between entries
Depth must be at least the largest conduit trade size. For a U-pull the rule is 6 × trade size plus the sum of the other conduits. These are minimum dimensions from NEC 314.28; manufacturer boxes are sized to meet them.
| Symbol | Meaning |
|---|---|
| d | Largest conduit trade size. |
| L | Minimum box length. |
8 × 2 = 16 inches minimum length, and the box must be at least 2 inches deep.
Continue with the Beam Deflection Calculator, Beam Load Calculator, Bending Stress Calculator, or the Wood Beam Span Calculator — or browse more structural & workshop and all construction calculators.
For a straight pull, the box length in the direction of the pull must be at least eight times the largest conduit trade size.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Estimate decking boards by length, screws, hidden fasteners and waste
Calculate concrete blocks needed for wall construction
Calculate full deck materials list including boards, joists, beams, posts, and cost estimates
Price hardwood the way the lumber yard does — by board footage.
Turn measured dimensions into the cubic yards concrete and gravel are sold in.
How many gallons it takes to cover an area at a given depth.
Content updated: September 2026