Home Wiring: Electrical Wiring and Cable Basics You Need to Know

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Wire Gauge

Wires come in different sizes/gauges to work with the amperage of the circuit in which they’re used. It’s counterintuitive, but the larger the number, the smaller the wire.

The most common sizes you’ll find in residential work are 14-gauge and 12-gauge. Larger appliances such as electric stoves, electric water heaters, electric dryers and central air units will often use 10-, 8- or even 6-gauge wire.

If you’re adding an outlet, you need to use wire the same gauge as the existing wiring. How do you tell your old wiring gauge? Here’s a simple visual.

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Family Handyman

Cable by the Numbers

An electrical cable is classified by two numbers separated by a hyphen, such as 14-2. The first number denotes the conductor’s gauge; the second denotes the number of conductors inside the cable.

For instance, 14-2 has two 14-gauge conductors: a hot and a neutral. This cable also contains a bare copper wire as the ground. Individual conductors are also color-coded, which tells you their purpose in the circuit.

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Outer Sheath Color Coding

The color of a cable’s outer sheath tells you the gauge of the wire inside the sheath as well as the amperage rating for the circuit.

WHITE = 14-gauge wire, 15-amp circuit

YELLOW = 12-gauge wire, 20-amp circuit

ORANGE = 10-gauge wire, 30-amp circuit

BLACK = 8- or 6-gauge wire, 45- or 60-amp circuits. Check sheath labeling for gauge and circuit specifics.

GRAY = Underground cable. Since all UF (underground feeder) cable is gray, check the sheath labeling for gauge and circuit specifics.