Conduit Fill Calculator

Conduit Fill Chart


A conduit fill chart can be used when access to online or computer-based tools (such as the Electrician Calculator Pro, which offers conduit size calculator, fill percentages, and more for your smart phone) are not available. These have the disadvantage that compared to conduit fill apps do not offer the flexibility of calculating different wire gauges and other perks, and can be slow and error-prone.

Typical Conduit Fill Chart

The following is a typical conduit fill chart, which shows data for different types of conduit such as EMT conduit, IMC conduit, and GRC conduit. The possible wire gauges go from 14 AWG to 750 MCM, and from conduit trade sizes of 1/2 inches to 4 inches.



How to use a conduit fill chart

The fill chart above allows you to determine how many wires can go inside a given conduit and not exceed a 40% fill rate.

If you have a fixed conduit type and size:

  1. Find the conduit type and size on the first column (for example, lets say we have a 1 inch EMT conduit).
  2. Find the wire gauge you require using the top row (for example, lets say we must use 10 AWG THHN wire).
  3. The intersection of the row and column indicates the maximum amount of wires that can be used (in this example, it would be 16 wires).

You can confirm this value using the online conduit fill calculator on our home page. It will indicate that the fill rate is 39.17%.