3-Way Switch Wiring Diagrams: 4 Common Layouts, Explained

3-way switch wiring connects two switches to one light so either switch can turn it on or off. Each 3-way switch has three terminals plus ground: one common terminal (usually the darker screw) and two traveler terminals. On the first switch, the common takes the incoming hot wire. On the second switch, the common sends power on to the light. Between the two switches run two traveler wires, which is why a 3-way circuit needs a 3-wire cable (black, red, white, plus bare ground) somewhere along the run. The white neutral never goes to a switch terminal: it runs to the light.

Where the power arrives (at a switch or at the light) changes which cable goes where, so there isn't one single 3-way switch wiring diagram. Below are the four layouts you'll find in most US homes, each mapped wire by wire.

Safety first. Turn off the power at the breaker and confirm it is off with a non-contact voltage tester before touching any wire, at both switch boxes and at the light. 3-way circuits often share boxes with other circuits. If what you find doesn't match one of these layouts, stop and call a licensed electrician.

How a 3-way switch works

A regular single pole switch simply opens or closes one wire. A 3-way switch is different: it has no ON or OFF position. Instead, it connects its common terminal to one traveler or the other.

• When both switches send power down the same traveler, the circuit is complete and the light is on.
• Flip either switch and the path moves to the other traveler, so the circuit opens and the light goes off.
• Flip either one again and the path lines up once more.

That's all there is to it. It's also why you can't tell a 3-way switch's position by looking at it: up can mean on or off, depending on the other switch.

The terminals on a 3-way switch

Terminal	Usual color	What connects to it
Common (COM)	Dark (black or bronze) screw	Incoming hot on the first switch; the wire to the light on the second switch
Traveler 1	Brass or light-colored screw	One of the two travelers between the switches
Traveler 2	Brass or light-colored screw	The other traveler
Ground	Green screw	Bare copper or green ground wire

Always check the label on the switch itself. Some devices mark COM in print instead of using a darker screw, and dimmers often use colored wire leads instead of screws.

Wire colors in a 3-way circuit

Wire	Usual job
Black	Hot, or the switched wire to the light
Red	Traveler (in a 3-wire cable)
Black in a 3-wire cable	Usually the second traveler
White	Neutral; sometimes re-marked with black or red tape when it's used as a hot or traveler
Bare copper or green	Ground

The re-marked white wire is the detail that confuses most people. In older 3-way layouts, a white wire is often used as a traveler or as the switched leg. It should be wrapped with black or red tape at both ends to show it isn't a neutral. If you see an unmarked white wire on a switch terminal, mark it before you disconnect anything.

Layout 1: power at the first switch, light at the end

This is the most common layout in houses wired in recent decades, and the easiest to follow.

Path: power → switch 1 → switch 2 → light

Box	Cables in the box	Connections
Switch 1	2-wire cable from the panel; 3-wire cable to switch 2	Incoming black → common. Red and black of the 3-wire cable → the two traveler terminals. Whites spliced together (neutral passes through). Grounds spliced, with a pigtail to the switch.
Switch 2	3-wire cable from switch 1; 2-wire cable to the light	Red and black from switch 1 → traveler terminals. Black of the 2-wire cable to the light → common. Whites spliced together. Grounds spliced, with a pigtail to the switch.
Light	2-wire cable from switch 2	Black → fixture hot. White → fixture neutral. Ground → fixture ground.

The neutral runs through both switch boxes, which is what current codes generally expect: most switch locations now need a neutral available in the box.

Layout 2: power at the first switch, light in the middle

Common in hallways and long rooms, where the light sits between the two switch locations.

Path: power → switch 1 → light box → switch 2

Box	Cables in the box	Connections
Switch 1	2-wire cable from the panel; 3-wire cable to the light box	Incoming black → common. Red and black of the 3-wire cable → traveler terminals. Whites spliced (neutral continues to the light).
Light	3-wire cable from switch 1; cable to switch 2	The two travelers are spliced straight through to switch 2 (red to red, black to black). The neutral from switch 1 → fixture neutral. The wire coming back from the common of switch 2 → fixture hot.
Switch 2	Cable from the light box	Travelers → traveler terminals. The return wire → common.

In older homes, the cable between the light and switch 2 is often a 3-wire cable, with the white wire re-marked as the return to the light. Newer work usually runs a 4-wire cable instead so a neutral is also available at switch 2. If you're adding a smart device or a dimmer that requires a neutral, check which one you have.

Layout 3: power at the light, switches beyond it

Typical of older houses, where the power was brought to the ceiling box first and then run down to the switches.

Path: power → light → switch 1 → switch 2

Box	Cables in the box	Connections
Light	Cable from the panel; cable to switch 1	Incoming white → fixture neutral. Incoming black → the wire going down to switch 1's common. The wire coming back from switch 2 → fixture hot.
Switch 1	Cable from the light; 3-wire cable to switch 2	Hot from the light → common. Red and black to switch 2 → traveler terminals. The return wire from switch 2 is spliced through to the cable going back to the light.
Switch 2	3-wire cable from switch 1	Red and black → traveler terminals. The remaining wire (often a re-marked white) → common, sending switched power back toward the light.

In the older version of this layout, the cable from the light to switch 1 is a 2-wire cable with its white re-marked as a hot, and neither switch box has a neutral. That's why some modern dimmers can't go into these boxes without rewiring. Treat this layout carefully: the colors don't mean what they usually mean, and labeling every wire before you disconnect it is essential.

Layout 4: one 3-way circuit, two or more lights

You can control several fixtures from the same pair of 3-way switches: a row of recessed lights in a hallway, or two pendants over a stair landing.

Path: power → switch 1 → switch 2 → light 1 → light 2 (and so on)

Box	Connections
Switch 1 and switch 2	Wired exactly as in Layout 1
Light 1	The switched black and the neutral from switch 2 are each spliced with a short pigtail to the fixture and with the cable continuing to light 2
Light 2 and beyond	Black → fixture hot, white → fixture neutral

The lights are wired in parallel: every fixture gets its own connection to the switched hot and to the neutral. Never chain fixtures in series. If you're putting dimmable LEDs on this circuit, add up the wattage of every fixture: it's the total that has to stay within the dimmer's range.

How to wire a 3-way switch step by step

These steps cover replacing an existing 3-way switch, the most common job. Running new cable between boxes is a job for an electrician.

1. Turn off the breaker and confirm the power is off at both switches and at the light with a voltage tester.
2. Remove the plate and pull out the old switch without disconnecting anything. Take a clear photo.
3. Find the common. Look for the darker screw or the COM marking, and wrap a piece of tape around the wire connected to it. This is the step that matters most.
4. Disconnect the two travelers. It doesn't matter which traveler goes on which traveler terminal of the new switch.
5. Connect the new switch: ground to the green screw, the taped wire to the common, the two travelers to the traveler terminals.
6. Fold the wires back, mount the switch and the plate, restore power and test from both locations, in every combination.

If the light only works when one switch is in a certain position, the common and a traveler are almost always swapped. Power off, and move the taped wire to the common terminal.

Adding a dimmer to a 3-way circuit

You can dim a light controlled from two places. The usual setup is one 3-way dimmer at one location and a regular 3-way switch at the other: the dimmer sets the level, and either location turns the light on and off. Don't put two standard dimmers on the same 3-way circuit unless the products are designed to work together.

Oxide's rotary dimmer comes in a 3-way version that does not require a neutral wire, which helps in older boxes like the one in Layout 3. It handles dimmable LED loads from 3W to 100W. For the full process, see our guide on how to install a dimmer switch.

3-way switches in solid brass

If you're replacing the switches at both ends of a staircase or hallway anyway, both locations deserve the same finish. Oxide makes 3-way toggles and dimmers on 2 mm solid brass plates, with a knurled brass lever on an ivory insert or a knurled brass rotary knob. Rated 15A 125V and made for standard US boxes, in Unlacquered, Aged or Satin Brass.

• 1-gang brass toggle switch: choose the 3-Way type for each end of the circuit
• 2-gang toggle switch: single pole + 3-way on one plate, for an entry where one light is also switched from upstairs
• 1-gang rotary dimmer switch, 3-Way version, to dim from one of the two locations
• All 3-way switches and dimmers

Not sure whether you have single pole or 3-way switches today? Our guide to single pole vs 3-way switches shows how to tell in a minute.

FAQ

How do I know which wire is the common on a 3-way switch?
It's the wire attached to the darker (black or bronze) screw, or the terminal marked COM. Tape it before you disconnect anything: getting the common right is the key to every 3-way switch wiring diagram.

Does it matter which traveler goes on which terminal?
No. The two travelers are interchangeable on standard 3-way switches. What matters is that the common wire goes on the common terminal.

Why does my 3-way switch only work when the other switch is in one position?
The common and a traveler have almost certainly been swapped on one of the switches. Turn the power off, identify the common wire at each switch, and move it to the common terminal.

Can I replace a 3-way switch with a single pole switch?
Only if you no longer want to control the light from two places, and the wiring has to be changed at both locations. If you want to keep two-location control, replace it with another 3-way switch or a 3-way dimmer.

Do both switches in a 3-way circuit need to be the same?
They both need to be 3-way devices. One can be a 3-way dimmer and the other a 3-way toggle. They don't need to match in style, but most people choose the same finish for both.

What cable do I need between two 3-way switches?
A 3-wire cable with ground (black, red, white and bare copper), because the two travelers run between the switches. In some layouts, a 4-wire cable is used so a neutral is also available. An electrician can tell you what your local code requires.