Pull Box Sizing Calculator
Size pull and junction boxes per NEC 314.28 for straight pulls, angle pulls, and U-pulls.
Results
Visualization
How It Works
NEC 314.28 sets minimum dimensions for pull and junction boxes based on the size and number of conduits entering them. Properly sized boxes allow safe wire pulling without damaging conductor insulation.
The Formula
Straight Pull: Length = 8 × Largest Conduit
Angle Pull: Distance = 6 × Largest + Sum of Others
U-Pull: Distance = 6 × Largest + 6 × Largest
Angle Pull: Distance = 6 × Largest + Sum of Others
U-Pull: Distance = 6 × Largest + 6 × Largest
Variables
- 8x — NEC multiplier for straight-through pulls
- 6x — NEC multiplier for angle pulls and U-pulls
- Largest — Trade size of the largest conduit entering the box
Example
Straight pull with 2-inch conduit: Minimum length = 8 x 2 = 16 inches. Angle pull with 2-inch and two additional 2-inch conduits on same wall: 6 x 2 + 2 x 2 = 16 inches.
Tips
- Straight pull boxes only need the 8x calculation in the direction of the pull.
- For angle pulls, the 6x calculation applies to each wall where conduits enter at an angle.
- Box depth is determined by the conduit locknuts and bushings, minimum 3 inches typically.
- Always provide adequate working space for conductors inside pull boxes.