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If you are an electrical contractor or IT installer, you already know that the wrong conduit size can turn a simple pull into a nightmare of snags, deformed jackets, and failed test results. This Cat6 conduit fill guide is built to answer the practical question on every job: how many data cables can you safely pull through each EMT or PVC size and still pass inspection and certification.

Whether you are feeding workstations, Wi‑Fi access points, security cameras, or IDF closets, following the NEC 40% fill rule helps you avoid overheated bundles, damaged cables, and expensive re‑pulls while leaving room for future circuits. The tables and tips below give you quick, job‑site‑ready numbers for Cat6 data cabling so you can quote accurately, size pathways correctly, and keep your crews moving.

Cat6 conduit fill chart (EMT)

Maximum Cat6 cables (approx. 0.24 in / 6.1 mm OD) in EMT conduit based on the 40% NEC fill limit.​

These values are based on typical Cat6 cable diameters; always check your specific cable’s OD and adjust if it is larger or smaller than 0.24 in. Metal conduit can increase attenuation slightly (2–3%), so only use EMT where required by exposure, protection, or code

Whether you’re running network cables above ceilings, behind walls, or underground, using the right size conduit ensures safe, efficient, and future-ready installations. Overfilling a conduit can damage your cables during pulls and cause overheating or signal loss. Underfilling means wasted material and space.

Conduits are a part of Horizontal pathway cabling and are used to keep the cable from resting on top of the false ceiling or being exposed if the ceiling is open. Due to this reason, sometimes there is a requirement to run cables in the Conduit. Without knowing how many cables can fit into a Conduit, it would be hard to estimate. You do not want to run a very large Conduit for a small bundle of data cables and at the same time, you don’t want the cables to not fit in a small Conduit.

This Cat6 Conduit Fill Guide helps you choose the correct EMT (Electrical Metallic Tubing) or plastic conduit for your Ethernet cable runs based on NEC-recommended fill capacities.

NEC Conduit Fill Rule (40% Limit)

The NEC establishes strict rules for the maximum cross-sectional area of a conduit that can be occupied by conductors. This is known as the conduit fill percentage and is found in NEC Chapter 9, Table 1.

• One Conductor: 53% fill.

• Two Conductors: 31% fill.

• Three or More Conductors: 40% fill (This is the standard limit for your application).

Since you are running six conductors, the conductors’ combined cross-sectional area cannot exceed 40% of the conduit’s total interior area.

🚫 Never run Ethernet cables in the same conduit as electrical wiring — it violates code and introduces signal interference.

Here is the Conduit Fill Guide which will help you use the optimal Metal or Plastic conduit to accommodate various categories of Network Cables. This table is based on the maximum number of cables permitted in the conduit and is calculated on the area of the cables with 40% of the conduit filled. Conduit should only be filled to a maximum of 60 percent, so this margin leaves you with room for future growth.

Remember, Attenuation values can also increase by 2 to 3 percent if the cable is installed in a metal conduit so install EMT Conduit only when necessary. Do not install data cabling in the same conduit as electrical wiring.

A conduit size with a diameter of .75 inches or a 3/4 inch Conduit can accommodate up to 6 Cat6 plenum-rated cables. This may vary from one manufacturer to another but as a thumb rule, the average is 6 Data cables with a 40% fill ratio capacity for the EMT Conduit.

1 inch EMT Conduit should fill approx 8 Data cables CMP

1.25 inch EMT Conduit – 15 Cat6 Cables

1.50 inch EMT Conduit – 20 Cat6 Cables

2.00 inch EMT Conduit – 35 Cat6 Cables

2.50 inch EMT Conduit – 60 Cat6 Cables

3.00 inch EMT Conduit – 80 Cat6 Cables

4.00 inch EMT Conduit – 120 Cat6 Cables

Tips for Pulling Ethernet Cables Through Conduit

Pulling Cables through the Conduit needs great skills and you need to make sure the Cable is not damaged or twisted. The most commonly used tool for pulling wire through the conduit is a fish tape, an electrician’s tool with a long, flat metal wire wound inside a wheel-shaped spool. A nylon string can also be used depending upon the location and situation.

Proper technique is critical to avoid damaging your network cable:

• Fish Tape: A spring steel tool ideal for most conduit pulls.
• Nylon Pull String: Useful for shorter or flexible runs.
• Use Lubricant: Consider cable lubricant for long or complex pulls.
• Avoid Sharp Bends: Maintain minimum bend radius (typically 4x cable diameter).
• Label Each End: Save hours of troubleshooting later.