12/2 MC cable is a 600V metal-clad branch-circuit cable with two 12 AWG conductors plus a green grounding conductor inside interlocking aluminum armor.
The spool looks interchangeable with any other 12-gauge cable, but the armor is the whole point. Type MC has its own article in the National Electrical Code — Article 330 — and its own fastening rules, its own grounding story, and its own limits. Get any of those wrong and an inspection fails before the drywall ever goes up.
What Is 12/2 MC Cable Made Of?
Type MC is a factory assembly of insulated conductors wrapped in interlocking metal tape armor or a smooth, corrugated metallic sheath, as defined in NEC Article 330. The “12/2” label tells you the conductor size and count, not the armor style — and the armor style is what changes from product to product.
A Southwire listing for its 12-2 stranded copper THHN cable with black, white, and green conductors lists 12 AWG wire, 19 strands per conductor, 20 mil insulation thickness, and a 0.504 in diameter over the armor. Solid-copper versions with interlocked aluminum armor run slightly thinner, landing around 0.460 in to 0.495 in outside diameter.
Inside the armor, a typical 12/2 assembly carries two circuit conductors — one black, one white — plus a separate green equipment grounding conductor. One manufacturer catalog describes the build as 12 AWG conductors, 600V rating, 90°C dry, THHN insulation, a polypropylene tape shield, and an interlocking aluminum strip armor.
Where 12/2 MC Cable Is Used And What It Cannot Do
Standard MC is a dry-location product unless it comes jacketed, and it is not rated to withstand physical damage. That single sentence kills most of the bad installations before they start.
- Good fit: branch circuits run through ceilings, joist bays, and stud cavities in dry interior spaces, where the armor gives mechanical protection conduit would otherwise provide.
- Bad fit: exposed spots where a forklift, ladder, or lawnmower can hit the run — standard MC is not a substitute for conduit in every location.
- Bad fit: wet or damp locations, unless the specific product is a jacketed version rated for it.
MC cable can be made with conductors from 18 AWG through 2,000 kcmil, so the family is broad. The minimum conductor size is 18 AWG copper, or 12 AWG aluminum and copper-clad aluminum. That range is exactly why two products both labeled “12/2 MC” can behave differently in the field.
12/2 MC Cable Specs, Sizes, And Costs
Conductor construction and armor type drive both the price and the application, so compare the assembly, not just the gauge count.
| Version | Key Detail | Typical Price |
|---|---|---|
| Stranded, w/ ground | 19 strands, 0.504 in over armor | $1.13/ft |
| Stranded, BLU/WHT/GRN | Color-coded conductors | $0.90/ft |
| Solid copper, aluminum flex | 2,500 ft barrel, no unit price shown | Call for pricing |
| Solid, interlocked aluminum armor | 0.460–0.495 in outside diameter | Varies by supplier |
| MC-VC (2 power + 16/2 control) | Different product family | $1.69/ft |
| Standard 12/2 MC | 600V, 90°C dry, THHN | Market rate |
| Jacketed 12/2 MC | Wet/damp location capability | Costs more |
Comparing quotes line by line is the only way to know whether you are buying the same thing twice. If you are weighing specific spools against each other, this roundup of tested 12 2 mc cable options walks through what actually ships in each box.
How Do You Secure And Ground 12/2 MC Cable?
MC cable must be secured and supported at intervals not exceeding 6 ft, and within 12 in of every box, cabinet, or fitting. Those two numbers are the ones inspectors check first.
The grounding question trips up more people than the fastening rule. On standard MC, the grounding path runs through the separate internal green or bare equipment grounding conductor — not through the armor itself. The aluminum armor is mechanical protection, so do not treat the jacket as your fault-current path.
One more caveat that costs real money: product pages vary on conductor construction and jacket type, so “12/2 MC” means different assemblies even when the gauge count matches. Interlocked aluminum armor, solid or corrugated sheath, and jacketed versions are not identical in application or protection level. Buy to the spec the job needs, not the one the label suggests. The NEC requirements for cables spell out the fastening, grounding, and location rules that apply.
FAQs
Can 12/2 MC cable be used outdoors?
Standard MC is a dry-location product, so it should not be run outdoors unless you are using a jacketed version rated for wet or damp locations. Rain, sprinkler overspray, and standing moisture break down an unjacketed assembly over time. Check the specific product listing before you commit to an exterior run.
Does the metal armor ground 12/2 MC cable?
No. On standard MC cable, the grounding path is the separate internal green or bare equipment grounding conductor, not the interlocking armor. The aluminum jacket provides mechanical protection for the conductors. Treating the armor as the grounding conductor is a common mistake that fails inspection and leaves the circuit without a proper fault path.
How often does 12/2 MC cable need to be secured?
MC cable must be secured and supported at intervals not exceeding 6 ft, and within 12 in of boxes, cabinets, or fittings. Those spacing limits come from the National Electrical Code and apply to standard installations. Tighter spacing is sometimes required by local amendments, so confirm with your local authority before rough-in.
References & Sources
- Southwire. “Arnorlite Type MC THHN/THWN Circuit Size Copper Conductor 120/208V Colors” Supports conductor size, strand count, insulation thickness, diameter, and weight specs.
- EC&M. “NEC Requirements for Cables” Supports fastening intervals, grounding path, and dry-location limitations for MC cable.
- Cerrowire. “MC Cable Specs” Supports Type MC construction details and product-family variations.
