Enter the area of one conductor and the number of conductors into the calculator to determine the conductor fill. This calculator can also evaluate any of the variables given the others are known.

Conductor Fill Formula

The following formula is used to calculate the conductor fill. Variables:

CF = (A * N) / T
  • CF is the conductor fill
  • A is the area of one conductor
  • N is the number of conductors
  • T is the total area of the conduit

To calculate the conductor fill, multiply the area of one conductor by the number of conductors. Then divide this result by the total area of the conduit.

What is a Conductor Fill?

A Conductor Fill refers to the percentage of a conduit or cable tray that is filled with conductors or cables. It is a crucial factor in electrical installations as it ensures safety and efficiency. Overfilling can lead to overheating and potential failure of the system, while underfilling can result in wasted space and resources. The National Electrical Code (NEC) provides guidelines on the maximum allowable conductor fill to prevent these issues.

How to Calculate Conductor Fill?

The following steps outline how to calculate the Conductor Fill using the formula CF = (A * N) / T.


  1. First, determine the area of one conductor (A).
  2. Next, determine the number of conductors (N).
  3. Next, determine the total area of the conduit (T).
  4. Finally, calculate the Conductor Fill (CF) using the formula CF = (A * N) / T.
  5. After inserting the values of A, N, and T into the formula, calculate the result.

Example Problem:

Use the following variables as an example problem to test your knowledge:

Area of one conductor (A) = 5

Number of conductors (N) = 8

Total area of the conduit (T) = 20