AWG Wire Gauge Chart: mm², Diameter & Resistance

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AWG / kcmil Used with: A gauge (AWG / kcmil)

Cross-section (mm²) Used with: A cross-section (mm²)

Worked example

These are example values. Change any entry above and press Calculate to run your own numbers.

Conductor	AWG 12
Cross-sectional area	3.3088 mm²
Circular mils	6.5299 kcmil
Diameter (solid equivalent)	2.053 mm (0.08081 in) stranded wire measures slightly larger over the strands
Copper resistance at 20 °C	1.588 Ω per 1,000 ft (5.211 Ω per km)
Aluminium resistance at 20 °C	2.604 Ω per 1,000 ft (8.542 Ω per km)
Copper mass	29.65 kg per km solid copper, 8,960 kg/m³

These figures come from the AWG definition and the standard resistivity of annealed copper, so they are exact for the model. Stranded conductors have a slightly higher resistance than a solid one of the same area because of the lay of the strands.

How it works

AWG (American Wire Gauge) numbers run backwards: a larger number is a thinner wire. The sizes follow a fixed geometric progression, so every three gauges halve the area and every six gauges halve the diameter. This page computes the figures from that definition and from the standard resistivity of copper.

The formulas

Diameter of gauge n: d = 0.127 mm × 92^((36 − n) ÷ 39)
Area: A = π ÷ 4 × d²
Circular mils: kcmil = (diameter in mils)² ÷ 1,000
Resistance: R = ρ × L ÷ A, with ρ(copper, 20 °C) = 1.7241 × 10⁻⁸ Ω·m
Every 3 gauges halves the area; every 6 gauges halves the diameter

Reference tables

AWG wire gauge chart, 4/0 to AWG 30

AWG	Diameter (mm)	Diameter (in)	Area (mm²)	kcmil	Cu Ω/1,000 ft	Cu Ω/km
AWG 4/0	11.68	0.46	107.2	211.6	0.04901	0.1608
AWG 3/0	10.4	0.4096	85.03	167.8	0.0618	0.2028
AWG 2/0	9.266	0.3648	67.43	133.1	0.07793	0.2557
AWG 1/0	8.251	0.3249	53.48	105.5	0.09827	0.3224
AWG 1	7.348	0.2893	42.41	83.69	0.1239	0.4066
AWG 2	6.544	0.2576	33.63	66.37	0.1563	0.5127
AWG 3	5.827	0.2294	26.67	52.63	0.197	0.6464
AWG 4	5.189	0.2043	21.15	41.74	0.2485	0.8152
AWG 5	4.621	0.1819	16.77	33.1	0.3133	1.028
AWG 6	4.115	0.162	13.3	26.25	0.3951	1.296
AWG 7	3.665	0.1443	10.55	20.82	0.4982	1.634
AWG 8	3.264	0.1285	8.366	16.51	0.6282	2.061
AWG 9	2.906	0.1144	6.634	13.09	0.7921	2.599
AWG 10	2.588	0.1019	5.261	10.38	0.9988	3.277
AWG 11	2.305	0.09074	4.172	8.234	1.26	4.132
AWG 12	2.053	0.08081	3.309	6.53	1.588	5.211
AWG 13	1.828	0.07196	2.624	5.178	2.003	6.571
AWG 14	1.628	0.06408	2.081	4.107	2.525	8.285
AWG 15	1.45	0.05707	1.65	3.257	3.184	10.45
AWG 16	1.291	0.05082	1.309	2.583	4.015	13.17
AWG 17	1.15	0.04526	1.038	2.048	5.063	16.61
AWG 18	1.024	0.0403	0.823	1.624	6.385	20.95
AWG 19	0.9116	0.03589	0.6527	1.288	8.051	26.41
AWG 20	0.8118	0.03196	0.5176	1.022	10.15	33.31
AWG 21	0.7229	0.02846	0.4105	0.8101	12.8	42
AWG 22	0.6438	0.02535	0.3255	0.6424	16.14	52.96
AWG 23	0.5733	0.02257	0.2582	0.5095	20.36	66.78
AWG 24	0.5106	0.0201	0.2047	0.404	25.67	84.21
AWG 25	0.4547	0.0179	0.1624	0.3204	32.37	106.2
AWG 26	0.4049	0.01594	0.1288	0.2541	40.81	133.9
AWG 27	0.3606	0.0142	0.1021	0.2015	51.47	168.9
AWG 28	0.3211	0.01264	0.08098	0.1598	64.9	212.9
AWG 29	0.2859	0.01126	0.06422	0.1267	81.83	268.5
AWG 30	0.2546	0.01003	0.05093	0.1005	103.2	338.5

Calculated from the AWG definition, so the finest gauges can differ from tables that round the diameter first by under 1%. Copper resistance is at 20 °C for a solid conductor. Current ratings (ampacity) are not shown because they depend on insulation rating, ambient temperature, installation and the electrical code.

Frequently asked questions

How do I convert AWG to mm²?

Use the chart or the calculator. AWG 20 is 0.518 mm², AWG 18 is 0.823 mm², AWG 16 is 1.31 mm², AWG 14 is 2.08 mm², AWG 12 is 3.31 mm², AWG 10 is 5.26 mm² and AWG 8 is 8.37 mm². To go from mm² to AWG, the converter finds the nearest gauge by area.

Why is a higher AWG number a thinner wire?

The gauge scale comes from the number of drawing steps needed to make the wire: each extra draw through a die makes it thinner and raises the gauge number. The scale is fixed so that gauge 36 is 0.005 inch and 4/0 is 0.46 inch, with a constant ratio between steps.

What is the resistance of AWG 12 copper wire?

About 1.588 Ω per 1,000 ft (5.21 Ω per km) at 20 °C. Resistance rises with temperature, by about 0.39% per °C for copper, and a stranded conductor has slightly higher resistance than a solid one of the same area.

Why does this chart not show ampacity?

Current rating is not a property of the gauge alone. It depends on the insulation temperature rating, the ambient temperature, how many conductors share a raceway, the installation method and the electrical code in force, so it comes from the code tables for your installation rather than a single column. Use the code and the cable maker's data for ampacity, and use this chart for geometry and resistance.

What is a kcmil?

A kcmil (also written MCM) is 1,000 circular mils, the unit used for conductors larger than 4/0. One circular mil is the area of a circle one mil (a thousandth of an inch) in diameter. A 250 kcmil conductor has about 126.7 mm² of copper.

AWG Wire Gauge Chart and Converter