12/2 wire has two live conductors without counting a grounding conductor. The correct size of conduit for a 12/2 cable is 1/2 inch. The most popular types of conduit used with this size of wire are PVC and EMT. You should opt for a larger size only if planning to run more than one 12/2 cable in a single conduit.

Let's break it down depending on the type of cable. 

Size Of Conduit For 12/2 Cable Depending on Type

12/2 NM-B Romex: PVC is the most common conduit size for NM-B Romex in residential settings. EMT can be used in commercial settings. A size 1/2 inch is perfect for a single 12/2 Romex. However, if you are running two cables at once, use 3/4" EMT. For PVC Schedule 40, two cables exceed the 31% fill limit for two conductors — use 1" PVC instead. 1/2" conduit fits one NM-B cable. When running multiple cables, note that NEC fill limits vary by cable count: 53% for one cable, 31% for two cables, and 40% for three or more cables.

12/2 UF-B Cable: The same rule about the conduit size applies to the UF-B cable. 1/2" is excellent for one cable. For two cables, use 3/4" EMT or 1" PVC Schedule 40. UF-B is not used too often because it is suitable for direct burial. When it does because of local code requirements, the common choice is PVC.

12/2 MC (Metal Clad) Cable: In a similar fashion to NM-B Romex and UF-B cable, 12/2 MC (Metal Clad) Cable uses a 1/2 inch conduit. If you wish to run multiple cables, consider using a 3/4 conduit. MC cable is not often used with conduits because it has armor. However, an MC cable can be used in a conduit for additional protection or aesthetics. For sleeve protection and protection of termination points or bends, EMT and flexible metal conduit can be used. Liquidtight Flexible Metal Conduit can be used if additional protection from moisture is required. PVC conduit is not common for MC cables as it does not provide many additional benefits compared to MC cables' own armor.

Individual 12 AWG THHN/THWN Conductors: THHN/THWN is used with conduit more often than any other type of cable. As there are no 12/2 THHN Cable, only single-conductors 12 AWG cables, you can fit more THHN cables into a 1/2 conduit. 

Therefore, you can fit up to nine single-conductor THHN conductors in a 1/2" EMT conduit and up to five in a 1/2" PVC Schedule 40 conduit. If you need a ground conductor with each circuit, 1/2" EMT fits three complete sets of two live conductors plus ground — nine total. A 1/2" PVC Schedule 40 conduit fits one complete set of two conductors plus ground, with two conductor slots to spare. RMC and IMC have the same interior dimensions as EMT and fit the same number of conductors.

When making a choice, remember to check the actual cross-sectional area of the cable according to manufacturer specs, as it may vary depending on the manufacturer.

 NNC sells all types of 12/2 cables suitable for conduit and all popular types of conduit that go with these cables. If you wish to calculate a precise kind of conduit for the particular electrical cable, visit our conduit fill calculator.