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Minimum Conduit Size Calculator
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# of ConductorsSize of ConductorsType of InsulationCalculated Area
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THWRHW
= RHW & RHW
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THWTHHN
= THHN & THWN
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THWTHW
= THW, TW, & THWN
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THWXHHW
= XHHW & XHH
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THWLV
= Low Voltage Cables
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THWFiber
= Fiber Optic Cables
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# of CablesSize of CableType of Cable
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LVEMT
= Electrical Metallic Tubing (Thinwall)
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LVENT
= Electrical Non-Metallic Tubing (Smurf Tube)
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LVFMC
= Flexible Metal Conduit
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FiberIMC
= Intermediate Metal Conduit
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FiberLFNC_A
= Liquidtight Flexible Non-Metallic Conduit Type A
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FiberLFNC_B
= Liquidtight Flexible Non-Metallic Conduit Type B
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========LFMC
= Liquidtight Flexible Metal Conduit (Sealtite)
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Total Area0.000RMC
= Rigid Metal Conduit (GRC)
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Conduit TypeEMTPVC-40
= Schedule 40 PVC (Plastic)
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Minimum Conduit Size
PVC-80
= Schedule 80 PVC (Plastic)
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Directions: Items in red color must be provided. Items in blue color are calculated. The top half of the calculator is for line voltage conductors while the bottom half is for low voltage and fiber optic cables. If you are doing line voltage, enter the total number of conductors of this size and insulation starting in cell B4. In cell C4, choose the conductor size from the drop down list. AWG sizes are shown as the number such as "12", "4", or "3/0". Kcmil or MCM are shown as the number such as "250", "500", or "750". Wire sizes must be between #14 AWG and 1000 Kcmil.
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If you are doing low voltage or fiber optics, enter the total number of cables of this type starting in cell B11. In cell C11, choose the cable type from the drop down list. Only a certain number of cable types are listed. Low voltage cables are in the format of (AWG)/(# of conductors). Their sizes are based on some typical industry sizes for stranded multi-conductor cables with shielding and a PVC jacket. Fiber optic cables are in shown as the number of fiber strands followed by an "f". Their sizes are based on Beldon riser or plenum series - whichever was larger for that number of fibers. You may wish to replace the values in the tables with areas of cabling you work with the most. Keep in mind that NEC 800.110 Exception states that conduit fill rules don't apply to communications wiring. Use this calculator as a general guide only.
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Once you have entered the quantity and size of the conductors, choose the insulation type in the "D" column to the right of the wire size. The insulation types must be picked from the drop down list provided. Note that these four insulation types cover nine different types as noted to the right of the calculation box.
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Finally, choose the conduit type from the drop down list. An explanation of the acronyms is listed to the right of the calculation box. If "N/A" appears in the Minimum Conduit Size in calculated cell E15, that means that that type of conduit is not manufactured large enough to legally contain the set of conductors that you have designated.
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This spreadsheet has been prepared and distributed by Design & Construction Engineers without cost or obligation. Design & Constructions Engineers makes no guarantee to the accuracy of the information contained or the results generated. The figures in the tables were taken from the tables found in the 2002 NEC. If you find errors or wish to report problems with this spreadsheet, please contact me via email at tstahlnecker@dcengineers.com so that I can make corrections and post them to our web site.
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