National Electrical Code: Number of Wires in a Box

Learn about the National Electrical Code for wiring. Find tips and information on counting wires in electrical boxes, number of conductors allowed in a wiring box, and more.

Oops, we're sorry. Something went wrong. Please try again later.
Oops, we're sorry. Something went wrong. Please try again later.
Share your take on this idea!
Upload your photo here.
CLOSE

Placing too many wires into an electrical box is difficult, dangerous, and against the National Electrical Code. To avoid possible shorts and overheating due to tightly packed wires, the code limits the number of wires you can put into an electrical box. Wires aren't the only things that count as wires, however.

continue reading below

Counting Wires in Electrical Boxes

Each item in your electrical box counts as a different amount of wires. Each insulated wire, all cable clamps combined, all uninsulated wires combined, and each support for light or other fixture count as one wire. Each switch, outlet, or other device counts as two wires. Jumper wires, however, count as zero wires. 

Number of Wires in a Switch Box

The switch box shown has a total of eight "wires" — one for each of the four insulated wires, two for the switch, one for all of the bare ground wires, and one for the cable clamps. The jumper wire does not count as a conductor. You'd need a 3x2x3-1/2-inch device box if you were wiring with 12-gauge wire.

Number of Conductors Allowed in a Wiring Box

This chart designates the number of conductors allowed in a wiring box based on your box size, the type of box, and the wire size.

Oops, we're sorry. Something went wrong. Please try again later.
Oops, we're sorry. Something went wrong. Please try again later.
Share your take on this idea!
Upload your photo here.
CLOSE

More Home Improvement

close
close
close
close
close

Loading... Please wait...

Add My Photo close
I Did It!
Share on Facebook
Uh oh! Please pick a jpg at least 600x600px.
Share on Facebook
Uh oh! Your photo failed to upload. Please try again or visit your profile.
No one has shared their photo yet.
close