How Many Outlets on a 20-Amp Circuit? (The Real NEC Answer)

NEC 220.14 · Receptacles · Updated 2026-08-07

Ask ten electricians how many outlets fit on a 20-amp circuit and you will hear ten, thirteen, and "as many as you want." Strangely, all of them are quoting real rules. For dwelling receptacle circuits, the NEC sets no maximum outlet count at all. The 13 and 10 figures come from the commercial calculation, and 8 to 10 is field practice, not code.

This guide traces every number to its source: the 180 VA per receptacle rule of NEC 220.14(I), the 80 percent continuous-load factor behind the famous 10-outlet figure, the dedicated 20-amp circuits every dwelling must have, and the wire size, voltage drop, derating, and box fill checks that matter more than the outlet count ever will.

The short answer

In a house, the NEC does not limit how many receptacle outlets go on a 20-amp circuit. Dwelling receptacles are folded into the general lighting load of 3 VA per square foot rather than counted one by one. In commercial and other non-dwelling work, NEC 220.14(I) assigns each receptacle 180 VA, which caps a 20-amp circuit at 13 receptacles, or 10 when the circuit serves continuous loads. Most electricians still plan homes around 8 to 10 outlets per circuit to avoid nuisance trips and to limit how much of the house one fault can darken.

Where 13 comes from: 180 VA per receptacle

In non-dwelling installations, NEC 220.14(I) assigns every receptacle strap a calculated load of 180 volt-amperes. A duplex receptacle sits on one strap, so it counts once, not twice. From there the ceiling is plain division. A 20-amp, 120-volt circuit supplies 20 x 120 = 2,400 VA, and 2,400 / 180 = 13.3, which rounds down to 13 receptacles. A 15-amp circuit supplies 1,800 VA, and 1,800 / 180 = 10 exactly.

The 80 percent rule: where the famous 10 comes from

The 13-receptacle ceiling assumes normal, non-continuous use. A continuous load is one expected to run for three hours or more, and NEC 210.19 and 210.20 require the circuit to be sized at 125 percent of it, which in practice limits the load to 80 percent of the breaker rating. On a 20-amp circuit that is 20 x 0.8 = 16 A, or 16 x 120 = 1,920 VA. Run the same division and 1,920 / 180 = 10.7, which rounds down to 10 receptacles. That is the honest origin of the widely quoted maximum of 10 outlets on a 20-amp circuit: the commercial calculation with the continuous-load factor already baked in. Planning for 10 instead of 13 simply builds in headroom.

Why houses are different

Dwelling receptacle outlets are not counted at 180 VA each. They fall under the general lighting load of 3 VA per square foot, so the code regulates total load rather than the number of straps on any branch circuit. The assumption is diversity: nobody runs a hair dryer in every bedroom outlet at once. That is why a whole bedroom, receptacles and lights together, can legally sit on one circuit.

One caveat before you wire a whole floor to one breaker: local amendments can add limits the NEC does not have. A few jurisdictions cap receptacles per circuit by local rule, and the inspector enforcing those amendments always has the final word. Check with your AHJ before you rough in.

The 20-amp circuits the NEC does require

While the NEC never caps outlets per circuit in a dwelling, NEC 210.11(C) does mandate several dedicated 20-amp circuits, and inspectors enforce these strictly.

These are floors, not ceilings. None of them limits how many receptacles sit on the circuit; they exist because kitchens, laundries, and garages host the appliances that pull sustained current.

Wire, breaker, and ground for a 20-amp circuit

A 20-amp circuit means 12 AWG copper minimum. NEC 310.16 lists 12 AWG copper at 20, 25, and 30 A in the 60, 75, and 90 degree C columns, but the small-conductor rule of 240.4(D) caps its overcurrent protection at 20 A no matter which column applies, just as it caps 14 AWG at 15 A and 10 AWG at 30 A. The equipment grounding conductor for a 20-amp circuit is also 12 AWG copper under 250.122. The full breakdown by breaker size lives in the wire size chart and the ground wire size chart.

The load math that actually matters

Whether a circuit is overloaded has nothing to do with faceplates and everything to do with what plugs into them. Eight receptacles at the commercial 180 VA figure total 8 x 180 = 1,440 VA, which is 1,440 / 120 = 12 A, only 60 percent of a 20-amp breaker. A single 1,500-watt space heater draws 1,500 / 120 = 12.5 A by itself, more than those eight allowances combined, and two heaters pull 25 A and trip the breaker no matter how few outlets the circuit has. Count watts, not wallplates.

Long runs: check voltage drop

Outlet count says nothing about wire length, and long home runs quietly eat voltage. The NEC recommends, in an informational note, keeping branch-circuit voltage drop near 3 percent, which is 3.6 V at 120 V. With the single-phase formula VD = (2 x K x I x L) / CM, K = 12.9 for copper, and 6,530 circular mils for 12 AWG, a 16 A load hits 3.6 V of drop at L = (3.6 x 6,530) / (2 x 12.9 x 16) = 23,508 / 412.8, about 57 feet one way. At 75 feet the drop is (2 x 12.9 x 16 x 75) / 6,530 = 30,960 / 6,530 = 4.74 V, just under 4 percent. Upsizing to 10 AWG (10,380 CM) brings it to 30,960 / 10,380 = 2.98 V, about 2.5 percent, with the breaker still 20 A. The voltage drop guide covers the full method.

Several circuits in one conduit: the derating trap

Home runs often share a raceway, and that is where a 20-amp circuit can quietly lose its legality. Under NEC 310.15(C)(1), more than three current-carrying conductors in one conduit forces an ampacity adjustment from the 90 degree C column for THHN. 12 AWG THHN starts at 30 A there: 4 to 6 conductors keep 80 percent (24 A), 7 to 9 keep 70 percent (21 A), and 10 to 20 keep only 50 percent (15 A). The first two still support a 20 A breaker after the 240.4(D) cap; the third does not. So four 2-wire 20-amp circuits, 8 current-carrying conductors at 21 A adjusted, are the most you can bundle before 12 AWG THHN falls below its breaker. Space is rarely the constraint, since 3/4 inch EMT holds 16 conductors of 12 AWG THHN per the conduit fill chart; it is derating that sets the real ceiling.

Box fill at every outlet

Every outlet is also a box fill calculation under NEC 314.16, where 12 AWG carries an allowance of 2.25 cubic inches per conductor. Take a mid-run receptacle with two 12/2 cables and internal clamps: four insulated conductors count 4 x 2.25 = 9.0 cu in, the device yoke counts two allowances at 4.5 cu in, all grounds together count one allowance at 2.25 cu in, and the clamps count one at 2.25 cu in. The total, 9.0 + 4.5 + 2.25 + 2.25 = 18.0 cubic inches, rules out shallow boxes entirely. The box fill guide covers every allowance type.

Common mistakes

• Treating 10 or 13 as a residential legal limit. Those numbers are the non-dwelling 180 VA calculation. In a house the NEC caps load, not outlet count.
• Running 14 AWG on a 20-amp breaker. 240.4(D) limits 14 AWG copper to 15 A protection, full stop. Every conductor on a 20 A circuit must be 12 AWG or larger.
• Putting lights or other rooms on the required circuits. Kitchen small-appliance, bathroom, and laundry circuits serve only their receptacles. A countertop receptacle sharing the lighting circuit fails inspection.
• Counting outlets instead of watts. Eight chargers and lamps are a rounding error; one 1,500-watt space heater is 12.5 A. Dedicate circuits to the heavy loads.
• Forgetting derating on shared home runs. Ten current-carrying 12 AWG THHN conductors in one conduit adjust to 15 A, which no longer supports a 20 A breaker.
• Ignoring box fill. Two 12/2 cables, a device, and clamps already demand 18.0 cubic inches, more than many common boxes hold.

How to plan a 20-amp receptacle circuit

1. List the actual loads: Note what will really plug in. Chargers, lamps, and clocks are a rounding error; heaters, window air conditioners, microwaves, and shop tools each need their own line item in amps.
2. Give heavy loads dedicated circuits: Anything that draws a sustained 10 A or more shares badly. Put it on its own circuit and keep the general receptacles for the light-duty plugs.
3. Apply the 8 to 10 rule of thumb: Not code, but sound practice: it spreads risk so one tripped breaker never darkens half the house. On 15-amp circuits, drop to 6 to 8.
4. Check the run length: Past roughly 57 one-way feet at a 16 A load, 12 AWG exceeds the 3 percent voltage drop recommendation. Upsize the conductor and keep the 20 A breaker.
5. Confirm with your AHJ: Local amendments can cap receptacles per circuit even though the NEC does not. The inspector's interpretation and the locally adopted code always govern.

Run the numbers before the inspector does. Conduit Fill & Bending Calc for iPhone and iPad puts wire size, voltage drop, ampacity with derating, box fill, and conduit fill in one place, built for the field, works offline, no account needed. When the question moves from how many outlets to which wire and which box, the answer is already in your pocket. Download Conduit Fill & Bending Calc on the App Store.

Frequently asked questions

How many outlets can I put on a 20-amp circuit in a house?

The NEC sets no maximum for dwelling receptacle circuits, because homes are covered by the 3 VA per square foot general lighting load rather than a per-outlet count. Common field practice is 8 to 10 outlets per circuit. Commercial installations are capped at 13 by the 180 VA rule.

What wire size do I need for a 20-amp circuit?

Use 12 AWG copper at minimum, and 12 AWG copper for the equipment ground as well. NEC 240.4(D) limits 14 AWG copper to 15 A overcurrent protection, so it can never sit on a 20 A breaker.

Can lights and outlets share a 20-amp circuit?

In most dwelling rooms, yes. The exceptions are the required dedicated circuits: kitchen small-appliance, bathroom, and laundry circuits may serve only their receptacles, with no lighting attached.

How many outlets can go on a 15-amp circuit?

The same logic applies: no hard NEC limit in dwellings, and 10 receptacles in commercial work, since 1,800 VA divided by 180 VA is exactly 10. In practice most electricians hold 15-amp circuits to 6 to 8 outlets.

Keep reading

• Wire Size & Ampacity Chart (NEC 310.16)
• Conductor Derating in Conduit (NEC 310.15)
• Box Fill Calculation Explained (NEC 314.16)