What Is Wire Gauge?
Gauge is a method of indicating thickness. Unlike most measurements, a gauge number is inversely related to thickness. The higher the gauge number, the thinner the material. Gauge is a measurement in jewelry, sheet metal, nails, electrical wire and more. In electrical wire, gauge indicates the diameter of the wire and is a factor in the electrical current the wire can safely carry.
Wire Gauge: Why It Matters With Electrical Wire
Matching electrical wire gauge to the current a device needs is critical for safety. Current that’s too high for a wire’s capacity — known as the wire’s ampacity — generates extra heat that the wire and it’s insulation is not designed to handle. Depending on the current and wire, the heat can melt the wire insulation, melt the wire itself or even start a fire. In addition, a wire gauge that doesn’t carry enough current for a device will reduce performance and can permanently damage the device.
While in general, larger-gauge wire carries more current safely, it’s also less flexible, so it’s more difficult to work with. And of course, it’s more expensive.
Wire Gauge for Electrical Projects
From the cables that carry power to your home to the wiring for your outlets and switches, wires for a house need to be able to carry a specific amount of current. Knowing the current different gauges can carry safely without overheating is necessary whether you’re replacing wiring or running new wiring. The National Electrical Code (NEC) specifies the wire gauge necessary for different levels of current.
Cable connectors, wire connectors and terminals have gauge ratings. Match them to the gauge of wire you’re working with.
Extension cords have gauge ratings as well. If a tool, piece of outdoor power equipment, etc. can use an extension cord, the device manual specifies the gauge and length options for the extension cord. Our guide, Choose the Best Extension Cord: Gauge Guides and More, shows you what types you need for your projects.
The AWG, or American Wire Gauge system, provides the standard in the United States for relating gauge numbers to specific diameters in inches. This standard helps ensure that when you buy or use wire of a particular gauge you know what the diameter is, and how much current it safely carries under specific conditions, according to the NEC. Here are some quick facts about the AWG:
- The AWG includes 44 wire sizes.
- The largest wire in the AWG standard is 0000-gauge wire with a diameter of 0.46 inches. This gauge is also known as 4/0 or 4-aught.
- The smallest wire in the AWG standard is 44-gauge wire with a diameter of 0.0031 inches.
- The AWG applies directly to solid wire — wire with only one strand. Stranded wire includes multiple, smaller wires bundled together. There are small spaces between each strand, so a stranded wire of a particular gauge will have a slightly larger diameter than a solid wire of an equivalent gauge.
- In addition to the AWG equivalent of the entire wire, stranded wire designations include the number of strands that make up the wire and the gauge of each. For example, 8-AWG 7/16 stranded wire indicates seven strands of 16-gauge wire equating to an 8-gauge wire.
Knowing the gauge of a wire will let you use wire strippers effectively. These tools have different gauges marked at a series of grooves on the jaws. Matching a wire to the groove for its gauge allows you to cut through the insulation without cutting the wire.
Wire Gauge Chart
Here’s an example of a wire gauge chart for some common wire gauges. This chart is for general reference only. Follow specifications and guidance in the electrical codes for your area.
If you’re unsure about any electrical work, contact a licensed electrician. Note that local codes may specify a licensed electrician handle wiring and electrical installations.
Wire Gauges for Electrical Cable
Electrical cable contains two or three current-carrying wires or conductors in addition to a ground wire. You’ll typically see the AWG number printed on the cable jacket along with the number of current-carrying conductors. For example:
- 12/2 or 12-2 with ground indicates two 12-gauge conductors and a 12-gauge ground wire.
- 6/3 or 6-3 with ground indicates three 6-gauge conductors and a 6-gauge ground wire.
Matching Wire Gauge to Devices
Here are some examples of wire gauges you might see for certain applications.
These are general tips only. Every electric device has specific current requirements. Multiple devices on an electrical circuit increase the amount of current the circuit needs to be able to carry. Wire choice should be based on electrical codes and the total amount of current needed. if you have any doubts about the electrical requirements of a device or the wire gauge necessary, contact a licensed electrician.
- 16-gauge wire is common in light-duty extension cords, speaker wire and some low-wattage lighting.
- 14-gauge wire is common in household lighting fixtures and lamps as well as some household outlets.
- 12-gauge wire is common in electrical outlets that might carry more current, such as outdoor outlets or those in a kitchen or bathroom.
- 10-gauge wire is common in circuits for some dryers, clothes washers and electric water heaters.
- 8-gauge and 6-gauge wire is common in circuits for kitchen ranges, wall ovens and standalone cooktops.
- 4-gauge wire might be used in furnace or central air conditioning circuits.
- 1/0-gauge and 3/0-gauge wire might be used for electrical service entrances in homes.
Our Electrical Wire and Cable Buying Guide explains wire, cable, naming conventions and more.