How to Wire an Outlet (Receptacle)

Wiring a standard receptacle comes down to three connections to the right terminals, but doing it well means understanding a few things the three-wire basics don't cover: whether the outlet is at the end or the middle of a circuit, why pigtailing is usually the better method, and how a GFCI's line and load terminals differ. This guide walks through the wiring method itself for a standard 120-volt receptacle. (If your goal is swapping out an existing worn outlet, the replacement scenario carries its own code-upgrade rules that are worth reviewing separately.) Above all, this is live electrical work, so the breaker goes off and stays off until you've proven the circuit dead.

Safety First

Turn off the breaker feeding the outlet, then confirm the circuit is dead with a non-contact voltage tester and a plug-in tester, testing again after you remove the cover plate, since one box can contain conductors from two circuits. A few conditions mean stopping and calling a licensed electrician instead of proceeding: aluminum branch wiring, an ungrounded metal box or no identifiable ground, cloth-insulated or knob-and-tube wiring, more cables in the box than you can confidently trace, or a circuit you can't positively identify and shut off. Many jurisdictions also require a permit, and new circuits are electrician work.

The Three Connections

Every standard receptacle has the same terminals, and matching wire to screw by color keeps it simple and safe.

The device has two brass screws on one side and two silver screws on the other, each pair joined by a break-off tab, plus a single green ground screw. The mnemonic is straightforward: brass is hot, silver is neutral (think “silver for the light-colored neutral”), and green is ground. Polarity matters here, because reversing hot and neutral energizes parts of a plugged-in device that are supposed to be neutral, a real shock hazard. On the outlet face, the wider slot is neutral, the narrower slot is hot, and the round hole is ground.

Use Screw Terminals, Not Backstab

Most receptacles have small push-in holes on the back, called backstab connections, that seem convenient. Don't use them. Their small spring contacts loosen over time and cause arcing, heat, and eventual failure, and they're a leading reason outlets go bad. Use the screw terminals instead: strip about three-quarters of an inch of insulation, bend the wire into a clockwise hook, loop it around the screw so tightening pulls the loop closed, and tighten firmly, then give each wire a gentle tug to confirm it's secure. Some quality devices offer a back-wire clamp, where a plate is tightened onto the conductor by the screw; that's excellent and completely different from a cheap backstab. Where you need to join conductors, use listed wire connectors.

End-of-Run vs Middle-of-Run

How many cables enter the box tells you which wiring situation you're in. An end-of-run outlet is the last device on the circuit, so only one cable enters the box: connect its one hot to a brass screw, its one neutral to a silver screw, and its ground to the green screw. Simple. A middle-of-run outlet passes power onward to other devices, so two cables enter the box, power in and power out, and that's where you have a choice to make.

Why Pigtail in the Middle of a Run

With two cables, there are two accepted methods. The first is to use both sets of screws, one hot on each brass screw and one neutral on each silver screw, letting power flow through the device's internal tabs to the downstream cable. It works, but it has two drawbacks: all the downstream current passes through the receptacle, and if the device fails, everything downstream loses power.

The better method is to pigtail: join both incoming and outgoing hot wires together with a short lead using a wire connector, and land that single lead on one brass screw; do the same for the neutrals to one silver screw; and join all the grounds with a lead to the green screw. Now the downstream circuit doesn't depend on this device at all, and no through-current runs across it. Pigtailing is the preferred practice for exactly these reasons. One more grounding note: in a metal electrical box, bond the ground to the box with its own pigtail as well as to the device; in a plastic box, the ground goes to the device only.

15-Amp vs 20-Amp Receptacles

Match the receptacle to the circuit it's on, which you identify by the breaker and the wire gauge.

A 20-amp circuit uses 12 AWG wire and can serve a 20-amp receptacle (recognizable by the sideways T-slot) or, when there are several receptacles on the circuit, standard 15-amp receptacles. A single receptacle alone on a 20-amp circuit must be rated 20 amps. The one thing you must never do is put a 20-amp receptacle on a 15-amp circuit, since that invites a load the 14 AWG wire can't safely carry.

Wiring a GFCI: LINE vs LOAD

A GFCI receptacle adds a wrinkle that causes the single most common wiring error. Its terminals are split into two pairs: LINE and LOAD. The incoming power from the panel must connect to the LINE terminals (black to brass-LINE, white to silver-LINE), which protects the GFCI itself. The LOAD terminals are optional and feed downstream outlets you want the GFCI to protect; connect the outgoing cable there only if you intend that feed-through protection.

Reverse line and load, and the GFCI won't reset and won't protect anything, the classic mistake. If you only want to protect this one outlet, use the LINE terminals and leave LOAD empty (and cover the unused terminals). For an ungrounded older circuit, the code allows a GFCI on the LINE terminals only, with the included “No Equipment Ground” and “GFCI Protected” labels applied.

The Break-Off Tab: Split and Switched Outlets

Those little tabs linking the two brass screws (and the two silver screws) are removable for a reason. Left intact, both halves of the outlet share one hot and one neutral, which is the normal setup. Break the brass tab and you can feed the two halves from two different hot wires, useful when you want the top outlet always on and the bottom switched, or the two halves on separate circuits. Break the tab only when you intend a split, and be careful with the neutral tab, especially on a multiwire branch circuit sharing a neutral, since breaking it unintentionally can cause problems. When in doubt, leave the neutral tab intact.

Finish and Test

In a dwelling, use a tamper-resistant device. Bring about a quarter inch of cable sheath into the box, don't overfill it (fold the conductors accordion-style rather than cramming them), seat the receptacle square, and fit the wall plate. Restore power and test with a plug-in receptacle tester, which confirms correct polarity and grounding at a glance, and if you installed a GFCI, press TEST to confirm it trips and RESET to restore it. Reversed hot and neutral is the most common DIY mistake, and the tester catches it instantly, so never skip this final step.

The Bottom Line

Wiring a receptacle is three connections, brass to hot, silver to neutral, green to ground, done well. Use the screw terminals rather than the backstab holes, and in the middle of a run, pigtail the hots, neutrals, and grounds so the downstream circuit never depends on the device. Match the receptacle's amperage to the circuit, wire a GFCI with incoming power on LINE and downstream loads on LOAD, and break the tab only for an intentional split. Prove the circuit dead before you start and test with a plug-in tester before you walk away. For anything involving aluminum wiring, an ungrounded box, or a new circuit, hand it to a licensed electrician.