Stub-Up Bend Calculator

A stub-up bend establishes a 90-degree rise from a conduit run to a box, enclosure, panel, or other raceway termination point. The critical layout number is the Bend mark from conduit end: the distance measured from the stated conduit-end reference to the mark that must be aligned with the bender’s applicable marking.

This Stub-Up Bend Calculator uses the finished rise requested in Desired stub height and the offset represented by Bender take-up. It produces a single field layout dimension for marking the conduit before the bend is made.

For the entered values:

• Desired stub height: 18 in
• Bender take-up: 4 in
• Bend mark from conduit end: 22 in
• Take-up used: 4 in

Mark the conduit 22 in from the specified reference end, align the actual bender marking for the selected bend method, and confirm the intended bend direction before applying force.

Stub-Up Layout Formula

The calculator applies the following field-layout relationship:

\(\text{Bend mark from conduit end} = \text{Desired stub height} + \text{Bender take-up}\)

The result is expressed in inches and is intended to be measured along the conduit from the reference end identified for the installation.

Field	Purpose
Desired stub height	The required finished stub height from the reference end
Bender take-up	The take-up value supplied by the bender or used by the selected field method
Bend mark from conduit end	The calculated location for the layout mark, measured from the conduit end
Take-up used	The bender take-up value carried into the calculation

The arithmetic does not identify a bender model, conduit trade size, raceway material, or bending convention. The entered Bender take-up must match the bender and layout method actually being used.

Calculation Example

For an 18-inch finished stub height with a 4-inch take-up:

\(18\text{ in} + 4\text{ in} = 22\text{ in}\)

The required mark is therefore:

\(\boxed{\text{Bend mark from conduit end} = 22\text{ in}}\)

The 22-inch dimension is not the finished stub height. It is the pre-bend layout mark used to position the conduit in the bender. After bending, verify that the finished 90-degree stub reaches the intended elevation and aligns with the box, coupling, connector, or raceway continuation.

Bender Take-Up and Reference End

Bender take-up represents the dimensional effect of the bending method used to produce the stub-up. It must be taken from the bender’s marking information or from a proven field method for that specific setup. A take-up value established for one hand bender, conduit size, or raceway type should not be assumed to apply to another.

The conduit-end reference must also remain consistent. If the finished stub height is measured from a box edge, fitting shoulder, slab surface, or another fixed point, use that same stated reference when measuring the calculated bend mark. Changing the reference point changes the installed geometry even when the arithmetic remains correct.

Field Verification

Before producing multiple pieces, make and check a first bend against the actual installation condition.

• Measure the calculated Bend mark from conduit end from the correct conduit end.
• Use the bender’s actual alignment indicator or the established field-method reference.
• Confirm whether the bend must rise, drop, face left, or face right before loading the conduit.
• Check the finished stub height after bending rather than relying only on the layout mark.
• Account separately for box position, fittings, couplings, raceway routing, and physical obstructions.

This calculation is a conduit-bending layout operation, not an NEC sizing calculation. It does not determine raceway fill, conductor ampacity, AWG or kcmil conductor size, voltage drop, branch-circuit or feeder loading, support spacing, bend-radius compliance, or installation acceptability. Those design and installation decisions must be evaluated separately for the actual raceway system and AHJ requirements.