How Many 12-2 Romex in 1 Conduit?

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Are you a homeowner looking to do some DIY electrical work? Or maybe you’re an electrician looking for the best way to wire your next project. 

Either way, this blog post is for you. 

We’ll cover the basics of how many 12-2 Romex cables can fit in one conduit and how to make sure everything is wired safely and correctly.

By the end of this blog, you should have a better understanding of how many 12-2 Romex can fit in one conduit.

What Is Romex?

Romex is a type of cable commonly used in residential wiring.

It is a flexible insulated cable consisting of two or more individually insulated conductors held together by an outer jacket. 

Romex is available in three different types: 12-2 (2 conductor) and 12-3 (3 conductor). 

It is also available in 14-2, 14-3 and 14-4, which are used for higher amperage circuits. 

Romex is designed to be run through standard electrical conduits and meets the National Electrical Code (NEC) standards for use in residential wiring. 

When using Romex with electrical conduits, it is important to make sure the conduit size is large enough to accommodate the number of cables being used. 

This can be determined by using the NEC conduit fill chart to calculate the allowable conduit fill capacities for each type of conduit.

Different Types Of Conduits

How Many 12-2 Romex in 1 Conduit?
How Many 12-2 Romex in 1 Conduit?

When it comes to conduits, there are a variety of materials and types available. 

The most common types of conduit used for running 12-2 Romex are PVC, EMT (Electrical Metallic Tubing), RMC (Rigid Metal Conduit) and FMC (Flexible Metal Conduit).

Each type of conduit has a different internal diameter which will affect the amount of wires that can be run through it. 

PVC conduit is the most cost-effective option and is very easy to work with, making it ideal for DIY projects. 

EMT conduit is lightweight and durable, making it an excellent choice for long runs or tight spaces. 

RMC is the heaviest type of conduit and is great for commercial applications or areas where extra protection is needed. 

Lastly, FMC offers the most flexibility and can be used in areas where bends or turns are needed.

Calculating Conduit Size For 12-2 Romex

Calculating the right conduit size for 12-2 Romex cables is an important part of any electrical project. 

The National Electric Code (NEC) requires that the conduit be large enough to accommodate the number of conductors it contains. 

To ensure that you have the correct conduit size, you must calculate the total area of all the cables, then add up the areas of all the individual cables and compare it to the NEC conduit fill chart. 

Generally, you will need a conduit size that is at least 1” for two 12-2 NM cables or 1-1/4” for two 12-2 UF cables. 

It’s important to note that these calculations do not take into account other factors such as outlets, boxes and bends in the conduit which may require a larger conduit size.

NEC Codes For Conduits Fill Capacity

How Many 12-2 Romex in 1 Conduit?
How Many 12-2 Romex in 1 Conduit?

The National Electric Code (NEC) provides guidelines for sizing conduit for cable. 

According to the NEC, the maximum fill is 53% of the space inside a conduit for one wire, and for two wires, the maximum fill is 43%.

The fill capacity is based on the type and size of the wire. 

Different types of conduits have different fill capacities and these can be found in a NEC conduit fill chart. 

It is important to calculate the conduit size for 12-2 Romex carefully to ensure that it meets all safety requirements. 

Additionally, if there are outlets or boxes in the conduit, more space may be needed to fit them in. 

When calculating conduit size for 12-2 Romex and other cables, it is important to consider the NEC codes and other factors to ensure a safe installation.

NEC Conduit Fill Chart

The NEC Conduit Fill Chart is a valuable tool for accurately determining how many conductors can be safely placed in a conduit.

This chart provides an easy-to-use reference for calculating the amount of allowable fill based on the type and size of conduit, as well as the size of the conductor. 

The chart takes into account the different types of conductors, such as THWN, THHN, AWG, and kcmil, as well as their respective sizes. 

This allows for accurate calculations when it comes to determining the size of conduit that is necessary for any given application. 

By using the NEC Conduit Fill Chart, it is possible to ensure that the maximum number of conductors can be safely placed in any given conduit without compromising safety.

Conduit Size For 12-2 NM Cable

For two 12/2 NM cable, the size of conduit required is 1 inch. 

This size is applicable for NM (non-metallic) cable and is based on NEC conduit fill calculations. 

NM cable is counted as one conductor and the fill chart must be consulted to determine the right conduit size. 

Any conduit installed outside is considered a wet location and NM (Romex) is not approved for wet locations. 

However, if the conduit is installed correctly, with appropriate sealing, it can be used in a wet location. 

Always check local building codes before installing any conduit or cable in a wet location.

Conduit Size For 12-2 UF Cable

When it comes to conduit size for a 12-2 UF cable, the size is 1-1/4 inches.

This is because of the dimensions of the cable which are 0.463 x 0.183. 

Using a fill chart based on the conduit type, it can be determined how many wires this size can hold. 

It is important to note that the NEC (National Electrical Code) specifies the maximum number of wires for any given conduit size. 

The NEC also provides a fill chart which allows you to easily calculate the size of conduit needed for any given combination of wires and/or cables. 

When considering outlets or boxes, it is also important to consider their size as they may take up additional space in the conduit.

Other Factors To Consider

When working with electrical wiring, it is important to keep in mind that there are other factors to consider beyond just the number of 12-2 Romex cables that can fit in a conduit. 

For instance, outlets and boxes should be taken into account in order to ensure that the wires are properly routed and protected.

It is also important to follow NEC codes for conduit fill capacity, as well as consult a conduit fill chart for specific information about how many wires can be safely installed in a conduit of a certain size. 

Furthermore, different types of conduits require different sizes for 12-2 Romex cables, with one-half inch being adequate for THHN wires plus ground unless the run is excessively long or there are too many 90-degree bends. 

Finally, any conduit installed outside is considered a wet location and NM (Romex) is not approved for wet locations.

Outlets And Boxes

How Many 12-2 Romex in 1 Conduit?
How Many 12-2 Romex in 1 Conduit?

When it comes to outlets and boxes, it is important to consider the number of wires that will be needed. 

The National Electrical Code states that the maximum number of wires allowed in an outlet box is 12.

Therefore, if you are using two 12/2 Romex cables in a conduit, you need to ensure that there is enough room for the two cables in the box. 

You may also need to use a larger box or outlet if you are using more than two 12/2 cables. 

Additionally, you should check with your local building code to ensure that your outlet or box meets all safety requirements.


In conclusion, when it comes to running 12-2 Romex through a conduit the size of the conduit is dependent on a few factors. 

The type of conduit, the number of bends, and the type of cable used will all affect how much space is needed. 

The National Electrical Code also provides guidelines on how many wires can fit into a conduit and what size conduit should be used for different types of cables. 

When in doubt, it’s always best to consult with a professional electrician to ensure that everything is done safely and up to code.

Best Wishes!

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About Charlie D Paige

Charlie is a massive DIY fan, with dozens of DIY projects under his belt - ranging from tiling to electrics, and concrete pads to walls. Charlie loves tinkering, seeing how things works, the outdoors and playing with power tools... so is it any wonder that he's completed so many DIY jobs over the years?

Charlie loves spreading his hard-won DIY experience with the world via this blog.