AWG Wire Gauge Chart

Diameter, cross-section and resistance for every American Wire Gauge size, with the NEC ampacity of building wire and a metric converter.

AWG numbers fall as wire gets thicker. 12 AWG is 2.05 mm across (3.31 mm²) and 10 AWG is 2.59 mm (5.26 mm²). Every 3 gauges doubles the copper area; every 6 gauges doubles the diameter.

American Wire Gauge chart, 4/0 to 40 AWG

d = 0.005 in × 92^{(36 − n)/39}
area = (1000 × d)² cmil = π ÷ 4 × d_mm² mm²
R = 10.371 × 1000 ÷ cmil Ω per 1000 ft (copper, 20 °C)

n is the gauge number, with 1/0 = 0, 2/0 = −1, 3/0 = −2 and 4/0 = −3. Every step of one gauge multiplies the diameter by about 1.123, so six steps double it and three steps double the area. The resistance column is for copper at room temperature; NEC Table 8 lists values at 75 °C, about 21% higher, and that is what the voltage drop calculator on this site uses.

Building wire: ampacity by gauge

For house wiring the question is usually how much current a gauge can carry. The answer depends on the insulation temperature rating and the terminals, which is why NEC Table 310.16 gives three columns. NM-B cable uses the 60 °C column.

Sizes larger than 4/0 are named in kcmil (thousands of circular mils): 250, 300, 350, 400 and 500 kcmil are the common service and feeder sizes.

Metric cable sizes and the nearest AWG

Which gauge for which job

Typical sizes in US homes and on job sites. They assume copper, short runs and the circuit breaker shown; long runs go one or two sizes up for voltage drop.

How gauge changes resistance and current

Because area changes by a fixed ratio between gauges, resistance does too: each step down in gauge number cuts resistance by about 20.6%, and each three steps cut it in half. That is why a 10 AWG run has roughly 63% of the resistance of 12 AWG and can carry the same load almost 60% farther for the same voltage drop. Ampacity does not scale so neatly, because a thicker conductor sheds heat through a surface that grows more slowly than its area; this is why the NEC table rises in uneven steps rather than doubling every three gauges.

Solid vs stranded

A stranded conductor of a given AWG has the same total copper area as the solid one, so ampacity is the same and resistance nearly so: NEC Table 8 lists 12 AWG copper at 1.93 Ω/1000 ft solid and 1.98 stranded. Stranded wire is larger in overall diameter and much more flexible, which is why it is required for 8 AWG and larger in conduit under 310.3(C) and preferred for anything that moves or vibrates.

Reading the gauge on a cable

NM-B jackets are color-coded by size in the US: white for 14 AWG, yellow for 12 AWG, orange for 10 AWG, and black for 8 and 6 AWG. The printed legend gives the full story: "12-2 W/G" means two 12 AWG insulated conductors plus a bare ground; "10-3" adds a red conductor for 240 V or multi-wire circuits.

Related calculators and charts

• Wire size calculatorChoose the gauge for a load, distance and voltage.
• Voltage drop calculatorCheck a gauge over your actual run length.
• What size wire for 50 amp6 AWG or 8 AWG, and when to go bigger.

Questions people ask