How do you size an angle pull or U pull box?

Under NEC 314.28(A)(2), start with 6 times the trade size of the largest raceway in that row and add the trade sizes of the other raceways on the same wall and row.

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Pull Box Tool

Pull Box Size Calculator

// SIZE PULL BOXES FOR STRAIGHT PULLS, ANGLE PULLS, AND U PULLS WITH NEC 314.28 FORMULAS AND FIELD-READY REMINDERS //

Box Inputs

Pull Scenario

Largest Raceway Trade Size

Other Raceways Same Row

For angle or U pulls, add the trade sizes of the other raceways on the same wall and row. Example: 2 in + 2 in = 4 in.

Box also contains splices or tapsThis does not change the NEC 314.28 bending-space formula, but it reminds you to check NEC 314.16 and NEC 300.14 as well.

Minimum Dimension

Minimum Wall-to-Wall Distance

24 in

NEC 314.28 controls bending space for pull and junction boxes with 4 AWG and larger conductors.

ScenarioStraight Pull

Formula8 × 3 = 24 in

Nearest Standard Box24 in

Straight pulls use 8 times the trade size of the largest raceway in the pulling direction.

Minimum code dimensions may pass inspection, but a larger box usually makes conductor pulling, training, and future maintenance easier.

NEC Rules

Use NEC 314.28(A)(1) when conductors pass straight through the enclosure without a change in direction. The minimum length in the pulling direction is 8 times the trade size of the largest raceway in that straight line.

Use NEC 314.28(A)(2) when conductors turn in the box or leave from the same wall. Measure from the raceway row to the opposite wall using 6 times the largest raceway in that row, then add the other raceway trade sizes on that same wall and row.

Straight pull: 8 x largest raceway trade size.

Angle pull: 6 x largest raceway + other raceways in the same row.

U pull: same base rule as angle pull, measured from the raceway row to the opposite wall.

If the enclosure also contains splices, taps, or devices, check NEC 314.16 and NEC 300.14 separately.

Code References

Use this calculator to set a minimum enclosure dimension, then verify the actual box layout, conductor bending, and local amendments before installation.

NFPA 70 National Electrical Code IEC overview

NEC references are for U.S. installations. IEC projects should verify the adopted local rules and enclosure product standard requirements.

Worked Examples

Scenario	Inputs	Formula	Minimum dimension	Practical takeaway
Straight pull	3 in raceway	8 x 3	24 in	A 24 in box is the minimum, but 30 in often pulls easier for large feeders.
Angle pull	3 in plus two 2 in raceways	6 x 3 + 2 + 2	22 in	The added raceway sizes are easy to miss and often cause inspection failures.
U pull	4 in plus one 3 in raceway	6 x 4 + 3	27 in	Many crews step up to a 30 in or 36 in box to reduce conductor damage risk.
Splice box reminder	6 insulated 12 AWG conductors with splice	Not a 314.28 formula	Use NEC 314.16 volume rules	A box can pass pull-box sizing and still fail box-fill checks.

Field Tips

Start with the largest raceway because it usually controls the box size.

For angle and U pulls, sum the other raceways in the same row on that wall before ordering the enclosure.

Use the next larger standard box when conductors are stiff, large aluminum, or part of a difficult pull.

If the box contains taps, splices, or devices, do a separate NEC 314.16 volume check.

Check conduit fill, voltage drop, and conductor length before freezing the enclosure layout.

NEC vs IEC Notes

IEC-based projects often reference IEC 60364 installation rules and enclosure standards such as IEC 60670 instead of NEC 314.28. Those systems may focus on bending radius, usable space, and product limitations rather than the same wall-to-wall formulas.

For mixed-specification projects, use this calculator as a planning check only. Confirm local raceway, enclosure, and conductor-bending requirements before fabrication or installation.

Pull Box FAQ

What is the NEC rule for a straight pull box?

NEC 314.28(A)(1) requires the dimension in the pulling direction to be at least 8 times the trade size of the largest raceway. A 3 in raceway needs 24 in.

How do I size an angle pull or U pull box?

Use NEC 314.28(A)(2): start with 6 times the largest raceway on that wall and add the trade sizes of the other raceways in the same row. A 3 in raceway plus two 2 in raceways needs 22 in.

Does NEC 314.28 replace box fill calculations?

No. NEC 314.28 checks bending and pulling space. If the box also contains splices, taps, or devices, you still need NEC 314.16 and NEC 300.14 checks.

Can conduit fill pass while pull box sizing fails?

Yes. A raceway can meet Chapter 9 fill rules and still need a larger pull box because large conductors need more room to bend and train safely.

When should I choose a box larger than the minimum?

Choose a larger box when the run includes 4 in or larger raceways, parallel sets, stiff aluminum conductors, or future service access needs. A 30 in box is often easier to work in than a 24 in minimum box.

Related Calculators

Conduit Fill Calculator

Calculate conduit fill percentage and select proper conduit size.

Box Fill Calculator

Calculate NEC 314.16 outlet, switch, and junction box fill volume.

Voltage Drop Calculator

Calculate voltage drop in electrical circuits for proper wire sizing.

Pull Box and Junction Box Sizing Guide

See the longer code explanation with straight-pull, angle-pull, and splice-box examples.

Use this result with the conduit fill, box fill, voltage drop, and wire sizing tools before you finalize an enclosure for feeders, service conductors, or long raceway pulls.