Wire gauge

Figure 1. A diagram showing different gauges of wire and their corresponding number based on its cross section.

Wire gauge measures a wire's cross sectional area. Knowing the gauge is important because it determines how much electric current a wire can carry without being damaged—this quantity is called ampacity.

American Wire Gauge System

The American Wire Gauge system or AWG standardizes the cross sectional area of a wires by assigning them an AWG number. As seen in Figure 1, a lower numbered gauge wire has a larger diameter and thus is able to carry higher currents. There are a total of 40 different gauge sizes with cross sectional areas ranging from 0.013 mm² to 107.22 mm² with their diameters changing incrementally between each gauge number.

Wire Gauge Values

The figures in the table below are taken from Table 310.15(B)(16) in the 2014 National Electrical Code (USA) and assume a temperature rating of 90°C. Also, Table 3.1 on page 69 in Introduction to Electricity was used as a template and reference.

AWG number	Cross sectional area (mm2)	Ohms/km (/km)	Ampacity (A)	Usage example
18	0.82	20.95	14	Low voltage lighting
16	1.31	13.18	18	Extension cords
14	2.08	8.28	25	Lighting fixtures
12	3.31	5.21	30	Kitchen appliances
10	5.26	3.28	40	Electric dryers
8	8.37	2.06	55	Electric ovens
6	13.30	1.30	75	Large electric heaters
4	21.15	0.81	85	Large furnaces
3	26.67	0.65	115	Large commercial wiring
2	33.63	0.51	130	Car battery cable
1	42.41	0.41	145	Power distribution
1/0	53.47	0.32	170	Power distribution
2/0	67.43	0.26	195	Power distribution
3/0	85.03	0.20	225	Power distribution
4/0	107.22	0.16	260	Power distribution
250	126.68	0.13	290	Power distribution
350	177.35	0.10	350	Power distribution
400	202.68	0.08	380	Power distribution

For a more complete list, please see Dr. Rowlett's unit page.

For Further Reading

For further information please see the related pages below:

• Wire
• Direct current
• Alternating current
• Electrical grid
• Or explore a random page!