TI-84 Conduit Bending Program & Online Calculator

TI-84 Conduit Bending Calculator Program & Math Guide

In commercial electrical installation, bending conduit (EMT, IMC, or Rigid) to bypass obstacles, run along walls, or terminate into electrical panels is a fundamental trade skill. Calculations for standard offsets, saddles, and 90-degree stub-ups are rooted in standard trigonometry.

While smartphone apps exist, vocational electrical schools (such as IBEW apprenticeship courses) and certification exams frequently require or allow TI-84 Plus / CE graphing calculators. This guide details the mathematical formulas behind conduit bending and provides a stable, field-ready TI-BASIC conduit bending program you can enter directly into your calculator.

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1. Trigonometry of Conduit Bending

Conduit bending is essentially solving right-angled triangles. Here are the core math formulas for the three most common bend configurations:

A. Offset Bends

An offset is used to shift a conduit run parallel to avoid an obstruction. It consists of two equal bends in opposite directions.

• Distance Between Marks ($D$): The distance between your first and second bend marks along the pipe depends on the height of the obstruction ($H$) and the bend angle ($\theta$): $D = \frac{H}{\sin(\theta)}$ Electricians often use standard "multipliers" in the field. These are the values of the cosecant function $\csc(\theta) = \frac{1}{\sin(\theta)}$:

  • 10-Degree Bend: Multiplier $\approx 6.0$

  • 22.5-Degree Bend: Multiplier $\approx 2.6$

  • 30-Degree Bend: Multiplier $\approx 2.0$ (Double the height)

  • 45-Degree Bend: Multiplier $\approx 1.414$

• Shrink ($S$): Bending a conduit diagonally shortens its overall straight-line run. To ensure your conduit terminates at the correct length, you must calculate and add this shrink value before cutting: $S = H \times \left( \frac{1}{\sin(\theta)} - \frac{1}{\tan(\theta)} \right)$

B. 3-Point Saddle Bends

A saddle is used to jump over a round obstruction (like another pipe). It features a center bend (usually 45°) and two outer bends (each half the angle of the center, i.e., 22.5°).

• Distance to Side Marks ($D_{\text{saddle}}$): The distance from the center mark to the two outer marks is: $D*{\text{saddle}} = \frac{H}{\sin(\theta*{\text{side}})} = \frac{H}{\sin(22.5^{\circ})} \approx H \times 2.6$

• Total Shrink ($S_{\text{saddle}}$): For a standard 45°/22.5° saddle, the total shrink is approximately $3/16$ inch per inch of obstruction height ($0.1875 \times H$).

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2. TI-BASIC Conduit Bending Program Code

Below is the optimized TI-BASIC code for the TI-84 calculator. The first line of the program forces the calculator into Degree mode to avoid formula errors.

PROGRAM:BEND
:Degree
:ClrHome
:Menu("CONDUIT BEND","OFFSET",1,"3-PT SADDLE",2,"STUB-UP",3,"EXIT",4)
:Lbl 1
:ClrHome
:Disp "--- OFFSET BEND ---"
:Input "OBSTACLE HT (IN): ",H
:Input "BEND ANGLE (DEG): ",A
:If sin(A)=0
:Then
:Disp "ANGLE CANNOT BE 0"
:Pause
:Goto 1
:End
:H/sin(A)→D
:H*(1/sin(A)-1/tan(A))→S
:ClrHome
:Disp "OFFSET RESULTS:"
:Disp "MARK DIST (IN):",D
:Disp "SHRINK (IN):",S
:Pause
:Goto 4
:Lbl 2
:ClrHome
:Disp "--- 3-PT SADDLE ---"
:Input "OBSTACLE HT (IN): ",H
:Input "CENTER BEND(45): ",C
:C/2→A
:H/sin(A)→D
:2*H*(1/sin(A)-1/tan(A))→S
:ClrHome
:Disp "SADDLE RESULTS:"
:Disp "DIST TO SIDE:",D
:Disp "TOTAL SHRINK:",S
:Pause
:Goto 4
:Lbl 3
:ClrHome
:Disp "--- 90 DEG STUB-UP ---"
:Input "DESIRED RISE(IN): ",R
:Input "BENDER DEDUCT(IN):",B
:R-B→M
:ClrHome
:Disp "STUB-UP RESULT:"
:Disp "MARK FROM END:",M
:Pause
:Goto 4
:Lbl 4
:ClrHome
:Disp "BENDING COMPLETE"

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3. How to Enter and Run the Program on Your TI-84

Follow these steps to create and run this calculator program on your physical TI-84 Plus / CE:

1. Create a New Program: Press the PRGM key, cursor right to the NEW menu, and press ENTER. Type BEND for the program name and press ENTER.

2. Enter Code: Type the TI-BASIC code line-by-line.

   • Control commands (like If, Then, Menu, Lbl, Goto) are found under PRGM $\rightarrow$ CTL.

   • Input/Output commands (like Input, Disp, ClrHome) are found under PRGM $\rightarrow$ I/O.

   • The store arrow → is typed by pressing the STO➔ button on the bottom left.

3. Exit and Run: Press 2nd $\rightarrow$ MODE (QUIT) to exit the editor. Press PRGM, select BEND under the EXEC menu, and press ENTER twice to run.

4. Test Calculations: Select OFFSET, input an obstacle height of 5 and an angle of 30. The calculator should output a mark distance of 10 inches and a shrink of 1.339 inches.