Pull Box Sizing Chart

Use this pull box sizing chart after the calculator result to document straight pulls, angle pulls, U-pulls, splices, raceway entries, bend radius, and cover access before selecting a listed enclosure.

Open calculator

Quick reference table

Pull box sizing starts with the pull geometry, not total wire count. Use the calculator worksheet to classify straight, angle, U-pull, splice, or cable-pull conditions, then verify enclosure dimensions, conductor bending space, cable radius, equipment instructions, adopted NEC requirements, and AHJ review.

Pull box sizing route classification

Pull box sizing route classification
Field condition	Record before calculating	Why it changes the box
Straight pull	Raceway trade size and opposite entry walls	Controls the straight pulling dimension
Angle pull	Raceways entering adjacent walls and spacing between entries	Requires wall and entry spacing checks
U-pull	Raceways entering and leaving the same wall	Spacing and wall dimension can control enclosure size
Spliced conductors	Conductor size, splice count, and bend space	Adds room for splices and conductor routing
Cable assembly pull	Cable outside diameter, minimum bend radius, and pull direction	Physical cable handling can exceed raceway-based dimensions

After the pull box calculator result

After the pull box calculator result
Result looks acceptable	Field check	Why it still matters
Minimum dimension found	Can the cover be opened and conductors worked safely?	Access can make a larger enclosure practical
Large raceways enter one side	Are locknuts, bushings, and fittings crowding each other?	Fitting layout can break a clean paper calculation
Splices included	Is conductor bending space and splice kit space documented?	Splice hardware occupies usable volume
Long pull planned	Does pulling tension require another pull point?	Mechanical stress can drive extra boxes

Formula basis

Pull box screen = identify pull type and controlling raceway size, then apply the calculator method for straight, angle, U-pull, splice, or cable bending conditions.

Pull type determines whether the worksheet follows straight, angle, U-pull, splice, or cable-bend logic.
Largest raceway size and entry wall locations often control the minimum enclosure dimensions.
Splices, cable outside diameter, and bend radius can require more space than a minimum raceway screen.

Worked examples

Angle pull with large conduitsDocument the largest raceway, each entry wall, entry spacing, and pull direction before the calculator result is compared with a listed enclosure.

Splice box in a feeder runA box that passes the pull dimension screen can still be too small for splice kits, conductor bending space, and future service access, so the worksheet should include splice hardware notes.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

This chart is a planning worksheet and does not reproduce pull box sizing code tables or text.
Listed enclosure dimensions, conductor bending space, cable bend radius, fitting layout, and field routing can change the final selection.
Minimum calculated dimensions are not a substitute for access, workmanship, manufacturer instructions, or AHJ review.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Verify the adopted NEC edition, listed enclosure dimensions, conductor and cable manufacturer data, local amendments, and the Authority Having Jurisdiction (AHJ) before final installation decisions.
Large conductors, splices, cable bend radius, pulling tension, cover access, and fitting layout may require a larger enclosure than a quick sizing screen suggests.

How to use this chart

1Classify the pull firstIdentify straight pull, angle pull, U-pull, splice condition, or cable assembly pull before entering dimensions in the calculator.

2Sketch every raceway entryRecord trade size, wall location, spacing, fitting layout, and pull direction so the calculator result reflects the actual route.

3Review access and bend spaceAfter the result, compare the selected enclosure with conductor bend radius, splice kit space, cover access, pulling equipment, and field installation room.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Draw the enclosure layoutSketch entry walls, raceway trade sizes, pull direction, splice locations, cover orientation, and equipment clearance before converting the sketch into calculator inputs.
Mark the controlling racewayIdentify the largest raceway and whether it participates in a straight, angle, U-pull, splice, or cable bending condition.
Verify enclosure selectionCompare calculator dimensions with a listed enclosure, conductor bend radius, splice space, cover clearance, and AHJ expectations.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Sizing a pull box from total wire count while ignoring whether the pull is straight, angle, U-shaped, spliced, or cable-radius controlled.
Forgetting cable bend radius, fitting crowding, and cover access after the minimum enclosure dimension appears acceptable.
Changing raceway entry walls in the field without rerunning the pull box calculation for the new geometry.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Why does pull type matter?

Straight pulls, angle pulls, U-pulls, splice boxes, and cable pulls use different space checks. The calculator needs the routing before it can size the enclosure.

Can a box be larger than the calculated minimum?

Yes. Larger boxes are often chosen for easier pulling, bend space, future work, splice kits, or manufacturer equipment requirements.

Should pull box sizing be checked with pulling tension?

Yes. A long or difficult route may need an extra pull point even when one enclosure size passes the geometric screen.