Conduit Offset Bending Estimator

Calculate the distance between bend marks and the estimated shrink for a two-bend conduit offset at 10, 22.5, 30, 45 or 60 degrees using standard field multipliers and shrink factors.

Trades & Construction

Bend Parameters

Obstacle Offset Depth (Inches)

Accepted range 0.1–100 in. An empty field is calculated as 1 in.

Bend Angle

Multipliers approximate the cosecant of the bend angle (the 10° value used here, 5.77, is slightly above csc 10° ≈ 5.76). Shrink factors are common field rules of thumb that run slightly below the trigonometric value tan(θ/2); actual shrink and gain vary with bender, conduit type and trade size, so confirm with a test bend.

Bending Marks

Distance Between Marks

(6" × 2)

Inches

Estimated Pipe Shrink1.5 inches

How to Mark: Measure from the conduit end to the obstacle and add the shrink (1.5"). Place the first mark there. Measure 12" back toward the conduit end for the second mark. Make both 30° bends in opposite directions so the offset is complete before the obstacle.

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Worked Example: 6 Inch Offset at 30 Degrees

Calculator default inputs, field multiplier method

Design Scenario

EMT running along a wall must step out 6 inches to clear a junction box. The obstacle starts 48 inches from the conduit end and two 30 degree bends will be used.

Design Parameters

Offset depth6 in

Bend angle30 deg

Multiplier2.00

Shrink per inch1/4 in

Mathematical Solution

1Distance between marks

6 x 2.00 = 12 in

2Estimated shrink

6 x 0.25 = 1.5 in

3First mark

48 + 1.5 = 49.5 in from the conduit end

4Second mark

Measured back toward the conduit end.

49.5 - 12 = 37.5 in from the conduit end

Engineering Conclusion: Bend 30 degrees at 37.5 in and 30 degrees in the opposite direction at 49.5 in. The offset adds 60 degrees to the run. For a 10 inch offset at 45 degrees the calculator gives 14.1 in between marks and 3.75 in of shrink.

What is Conduit Offset Bending?

An offset is two equal bends in opposite directions that move a conduit run sideways to clear an obstacle or enter a box. The two marks form the hypotenuse of a right triangle whose opposite side is the offset depth, which is why the multiplier is the cosecant of the bend angle.

Mathematical Foundation

Distance between bend marks

D = H \times M \qquad M \approx \csc \theta = \frac{1}{\sin \theta}

H

= Offset depth: the perpendicular distance the conduit must move (in)

\theta

= Bend angle used for both bends (degrees)

M

= Field multiplier for the bend angle (10: 5.77, 22.5: 2.61, 30: 2.00, 45: 1.41, 60: 1.15)

Estimated shrink

S = H \times s_{\theta}

s_{\theta}

= Field shrink per inch of offset (10: 1/16, 22.5: 3/16, 30: 1/4, 45: 3/8, 60: 1/2)

S

= Amount the conduit run shortens because of the offset (in)

Laws & Principles

NEC 2023 358.26, 344.26 and 352.26 limit bends to 360 degrees total between pull points for EMT, rigid metal conduit and PVC.
NEC 358.24 and the matching sections require bends to be made without damaging the conduit or reducing its internal diameter.
Shallower offset angles add fewer degrees to the run and lower pulling tension compared with steeper angles.
Field multipliers are rounded; bender-specific values from the manufacturer take precedence.

Step-by-Step Example Walkthrough

" A conduit must step 10 inches off a wall using two 45 degree bends. "

1. Distance between marks: 10 x 1.41 = 14.1 in.
2. Estimated shrink: 10 x 3/8 = 3.75 in.
3. Degrees added to the run: 2 x 45 = 90 degrees.

Final Result: Marks 14.1 in apart with about 3.75 in of shrink; the offset uses 90 of the 360 degrees allowed between pull points.

Quick Answer

Multiply offset depth by the multiplier for the bend angle to get the distance between marks, and by the shrink factor to find how much the run shortens. A 6 inch offset at 30 degrees needs marks 12 inches apart with about 1.5 inches of shrink.

Scope and safety: Results are layout aids based on rounded field values. Follow the bender manufacturer instructions, confirm with a test bend, and use appropriate caution and protective equipment when bending conduit.

Multiplier and Shrink Reference

Bend angle	Calculator multiplier	csc(theta)	Field shrink per inch	tan(theta/2)
10 deg	5.77	5.759	1/16 (0.063)	0.087
22.5 deg	2.61	2.613	3/16 (0.188)	0.199
30 deg	2.00	2.000	1/4 (0.250)	0.268
45 deg	1.41	1.414	3/8 (0.375)	0.414
60 deg	1.15	1.155	1/2 (0.500)	0.577

The tan(theta/2) column is the shrink for an idealized sharp-corner offset. Real bends have a radius, so actual shrink varies with the bender; the field values are the conventional layout figures. A 6 inch offset at 10 degrees gives 34.62 in between marks with the calculator multiplier versus 34.55 in with csc 10 degrees.

Frequently Asked Questions

What is a conduit offset multiplier?

It is the factor that converts offset depth into the distance between the two bend marks. It approximates the cosecant of the bend angle, so a 30 degree offset uses 2.00 and a 6 inch offset needs marks 12 inches apart.

What is shrink and how do I use it?

Shrink is the amount the conduit run shortens because part of its length travels diagonally through the offset. When bending toward an obstacle, add the shrink to the measured distance from the conduit end to the obstacle to place the first mark, then measure the mark spacing back toward the conduit end for the second mark.

Which bend angle should I choose?

Shallower angles (10 or 22.5 degrees) make a longer, gentler offset that adds less bend to the run and pulls more easily. Steeper angles (45 or 60 degrees) fit tight spaces but add more degrees toward the 360 degree limit between pull points. A 30 degree offset is a common compromise because its multiplier is 2.

How many degrees does an offset add to the run?

Each offset has two bends, so a 30 degree offset adds 60 degrees and a 45 degree offset adds 90 degrees. NEC 2023 358.26 and the matching sections for other raceways limit the total to 360 degrees between pull points.

Why does my bend not match the calculator exactly?

Multipliers and shrink factors are rounded field values. Bender shoe radius, conduit springback, trade size and how marks are aligned on the bender all affect the result. A test bend on scrap conduit is the most reliable check.

Related Calculations

Calculation Provenance & Validation Record

Method

Multiplies offset depth by the field multiplier for the chosen angle to get the distance between bend marks, and by the field shrink factor to estimate run shortening.

Formula

D = H imes M_{ heta} qquad S = H imes s_{ heta}

Assumptions

Both bends use the same angle and are made in opposite directions on the same plane.
Multipliers approximate the cosecant of the bend angle; the 10 degree value used (5.77) is slightly above csc 10 degrees (5.759).
Shrink factors are common field rules of thumb and run below the sharp-corner geometric value tan(theta/2); actual shrink depends on bender radius, conduit type and trade size.
Results are layout aids. Confirm with a test bend for the bender in use.

References

NFPA 70, National Electrical Code (NEC 2023) 358.24 and 358.26 - EMT bends and the 360 degree limit between pull points (similar rules in 344.24/344.26 and 352.24/352.26)
Bender manufacturer instructions - multiplier, shrink and gain values for specific benders
Right-triangle trigonometry: hypotenuse = opposite side / sin(theta)

Last substantive review: 2026-10-03

Automated test status: 5 golden test vectors passing (COB-01, COB-02, COB-03, COB-04, COB-05)

Method, assumptions & governing standards

Standard Sourced

Calculation Methodology

Multiplies offset depth by the field multiplier for the chosen angle to get the distance between bend marks, and by the field shrink factor to estimate run shortening.

Governing Standard NECA 101-2020 / 2023 NEC

Standard:NECA 101 / NFPA 70 (NEC)

Statutory building, electrical, and mechanical codes vary by jurisdiction. Confirm local municipality amendments before installation.

Key Assumptions & Constraints

Both bends use the same angle and are made in opposite directions on the same plane.
Multipliers approximate the cosecant of the bend angle; the 10 degree value used (5.77) is slightly above csc 10 degrees (5.759).
Shrink factors are common field rules of thumb and run below the sharp-corner geometric value tan(theta/2); actual shrink depends on bender radius, conduit type and trade size.
Results are layout aids. Confirm with a test bend for the bender in use.

Regression Tests: 5 golden vectors

Last Verified: 2026-10-03

Primary References: 3 documented

Field Trade Notice: For trade planning and engineering estimates. Final installations must conform to project blueprints, authority having jurisdiction (AHJ) code approvals, and site-specific inspections.