10/2 Romex is a 600-volt NM-B cable with two 10-gauge copper conductors plus a bare ground, used mainly for 30-amp indoor circuits like dryers and water heaters.
For the full breakdown, see our best 10/2 Romex Wire guide.
A 240-volt dryer that trips its breaker on every cycle, a water heater that needs a dedicated run back to the panel — these jobs ask for a cable fat enough to carry 30 amps without heating up. 10/2 Romex answers that call, but the name itself hides a detail that trips up more DIYers than any other part of the job: it carries three conductors, not two. The breakdown, the amp rating, and the places it must never go are all below.
What The Numbers 10 And 2 Actually Mean
The “10” is the conductor gauge and the “2” counts only the insulated current-carrying wires — a bare ground wire rides along that the label never mentions. Southwire’s Type NM-B product family lists this cable as 10 AWG, 2 conductor, solid copper with a bare ground, which is why the cable in your hand has three visible wires even though the spool says 2.
- Black and white: the two insulated 10 AWG conductors carrying hot and neutral.
- Bare copper: the equipment ground, uninsulated and counted separately.
- Wrap: the outer NM-B jacket that binds all three together.
Sellers make this more confusing by listing it as 10-2 or 10/2, sometimes with the words “with ground” tacked on and sometimes without. Both labels describe the same cable.
What Is 10/2 Romex Wire Used For?
10/2 Romex feeds 30-amp residential circuits — mostly the heavier 240-volt appliances that need more current than a standard 15- or 20-amp run provides. The cable’s 600-volt rating and 90°C temperature ceiling fit normally dry indoor spaces, which covers the bulk of a home’s wiring.
Common loads on a 10/2 run include electric dryers, electric water heaters, 30-amp EV chargers, window air conditioner disconnects, and hot tub sub-feeds. A dedicated 30-amp circuit back to the breaker panel is standard for each of these, and the wire gauge has to match the breaker — 10 AWG copper pairs with a 30-amp breaker, not a 40.
If you’re comparing cable brands and spool lengths before a project, this roundup of tested 10 2 romex wire options covers what’s worth buying.
Specs At A Glance
Southwire’s published specs for its 10-2 NM-B cable give a clear picture of what’s inside the jacket and how much the run will weigh.
| Spec | Value | Notes |
|---|---|---|
| Conductors | 2 solid copper, 10 AWG | Plus 1 bare ground |
| Voltage rating | 600 V | NM-B family rating |
| Insulation thickness | 20 mils (0.51 mm) | Per Southwire specs |
| Jacket thickness | 25 mils (0.64 mm) | Outer NM-B wrap |
| Approx. outside dimensions | 0.505 x 0.218 in | Flat oval profile |
| Copper weight | 91 lbs per 1,000 ft | Conductor copper only |
| Approx. total weight | 126 lbs per 1,000 ft | Includes jacket |
| Temp / location rating | 90°C, dry indoor only | Not for wet or buried runs |
Where 10/2 Romex Cannot Go
NM-B cable is built for normally dry indoor locations and is not rated for wet spots or direct burial — Southwire’s own listing marks both “Direct Burial” and “Wet Location Use” as No. Running 10/2 through a damp crawlspace, burying it underground, or exposing it to weather will fail inspection and shorten the cable’s life.
Outdoor and buried runs need a different product: UF-B cable for direct burial, or NM-B pulled through conduit where allowed. Check Southwire’s 10-2 NM-B product page for the full spec sheet and the current model numbers before ordering.
Three more traps to watch for. First, the ampacity figure that pairs 10 AWG copper with 30 amps comes from the 60°C column of NEC Table 310.16, and your terminations and local code edition may change what’s allowed. Second, 10/2 is not automatically correct for every 30-amp load — read the device instructions and confirm breaker sizing. Third, spools come in several lengths, and Southwire lists 15 ft, 50 ft, 100 ft, 250 ft, and 1,000 ft versions of the same cable, so match the footage to your run before you buy.
FAQs
Does 10/2 Romex have three wires or two?
It has three. The two insulated 10 AWG conductors carry hot and neutral, and a bare copper ground runs alongside them inside the same jacket. The “2” on the label counts only the insulated wires, which is why the cable looks like it has more wires than the name suggests.
Can 10/2 Romex be used outdoors or underground?
No. Southwire lists 10-2 NM-B as dry-location indoor cable with direct burial and wet location use both marked No. Outdoor or buried runs call for UF-B cable, or NM-B run inside conduit where local code permits it. Check your local rules before assuming a route is allowed.
What size breaker goes with 10/2 Romex?
A 30-amp breaker is the standard pairing for 10 AWG copper on a 30-amp circuit. The exact ampacity depends on the temperature rating of your terminations and the NEC edition your area follows, so confirm both against the device instructions and your local inspector before wiring the circuit.
References & Sources
- Southwire. “Romex SIMpull Copper Type NM-B Cable, 10-2, 1000 ft” Supports conductor count, ground wire, 600 V rating, indoor dry-location limits, and dimensional specs.
- Southwire. “Romex SIMpull Copper Type NM-B Cable, 10-2, 250 ft” Confirms 10 AWG, 2-conductor solid copper construction with a bare ground in a shorter spool length.
- Southwire. “Romex SIMpull Copper Type NM-B Cable, 10-2, 15 ft” Confirms the 90°C dry-location temperature rating and the short-length product variants.
