Wire Gauge Calculator

Look up the diameter, area, resistance and typical current rating of any AWG wire size, and find the resistance of a given length. Example: 12 AWG copper is 0.0808 inches (2.05 mm) across, has 3.31 mm squared of area, 1.588 ohms per 1,000 feet and carries about 25 amps at 75 C.

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Wire size (AWG)

Wire length

feet

How to use the Wire Gauge Calculator

Choose the AWG wire size.
Enter a wire length to see its total resistance.
Press Calculate for diameter, area, resistance and ampacity.

Formula and method

Diameter in inches = 0.005 x 92^((36 – n) / 39), where n is the AWG number (use 0, -1, -2, -3 for 1/0 to 4/0). Area = pi / 4 x diameter squared. Resistance = resistivity x length / area, with copper resistivity of 1.724 x 10^-8 ohm-meters.

Worked example: 12 AWG

Property	Value
Diameter	0.0808 in (2.053 mm)
Area	3.31 mm2
Resistance	1.588 ohms per 1,000 ft
Ampacity (75 C)	25 A

AWG size chart

AWG	Diameter (in)	Area (mm2)	Ohms per 1,000 ft
18	0.0403	0.82	6.385
16	0.0508	1.31	4.015
14	0.0641	2.08	2.525
12	0.0808	3.31	1.588
10	0.1019	5.26	0.999
8	0.1285	8.37	0.628
6	0.1620	13.30	0.395
4	0.2043	21.15	0.248
2	0.2576	33.63	0.156
1	0.2893	42.41	0.124
1/0	0.3249	53.48	0.098

Why smaller numbers are thicker

AWG counts the drawing steps used to make wire, so a higher number means thinner wire. Every 6 gauges doubles the diameter, and every 3 gauges doubles the area.

Frequently asked questions

What is AWG?

American Wire Gauge, a standard for round wire sizes.

Is a lower AWG thicker?

Yes. 10 AWG is thicker than 14 AWG.

How many amps can 12 AWG carry?

About 20 amps on a typical circuit, 25 A by the 75 C table.

What is the diameter of 14 AWG?

0.0641 inches (1.63 mm).

How do I find resistance of a wire?

Resistivity times length divided by area; or use the ohms per 1,000 feet value.

Does aluminum differ?

It has about 64% higher resistance than copper.

Sources

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