Conduit Fill Calculator
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RESOURCES AND CHARTS

NEC CONDUIT FILL CALCULATOR

NEC
Utility

Conduit

Conductors

1

+ -

Maximum Allowed
Conductors In Conduit

0

Our NEC Conduit Fill Calculator tool determines the appropriate size of electrical conduit needed to safely encase electrical wires in a building. To use it, enter conduit type and then conduit size. You will get wire type and size as per NEC or utility and the number of conductors.

How do you calculate conduit fill?

To calculate conduit fill:

  1. Select conduit type and size.
  2. Count the wires and note their gauge.
  3. Use NEC tables to find the total area of wires.
  4. Ensure this area is at most 40% of the conduit's total area.

What is the fill rate for conduit? 

For conduit fill, the NEC allows a maximum fill of 40% for more than two wires, 31% for two wires, and 53% if only one wire is used.

Why is conduit fill rate important?

Conduit fill is essential to prevent overheating and ensure safe electrical operation by avoiding overcrowding of wires within a conduit.