Battery building tools/Reference

AWG to mm².
See the size behind the number.

Convert wire gauge to conductor area or diameter. The chart covers 4/0 through 40 AWG, with the units side by side.

Conductor cross-section

Round conductor equivalent.
Insulation is not included. Drawing is not life size.

Wire gauge / metric reference

What is on your cable label?

Conductor area3.309 mm²

Conductor diameter2.053 mm

0.08081 inches

Lower AWG numbers mean a thicker conductor. 1/0, 2/0, 3/0 and 4/0 continue the scale beyond 1 AWG.

3.309 square millimetres area, 2.053 millimetres diameter.

The reference table

AWG to mm² and mm chart

Select a gauge to load it into the converter. Area and diameter describe the conductor, before insulation.

Find a gauge or metric value

Nominal AWG geometry and calculated annealed-copper resistance at 20 degrees Celsius.
Area mm²	Diameter mm	Diameter inches	Copper resistance Ω/km at 20 °C
107.2	11.68	0.46	0.1608
85.03	10.4	0.4096	0.2028
67.43	9.266	0.3648	0.2557
53.48	8.251	0.3249	0.3224
42.41	7.348	0.2893	0.4066
33.63	6.544	0.2576	0.5127
26.67	5.827	0.2294	0.6464
21.15	5.189	0.2043	0.8152
16.77	4.621	0.1819	1.028
13.3	4.115	0.162	1.296
10.55	3.665	0.1443	1.634
8.366	3.264	0.1285	2.061
6.634	2.906	0.1144	2.599
5.261	2.588	0.1019	3.277
4.172	2.305	0.09074	4.132
3.309	2.053	0.08081	5.211
2.624	1.828	0.07196	6.571
2.081	1.628	0.06408	8.285
1.65	1.45	0.05707	10.45
1.309	1.291	0.05082	13.17
1.038	1.15	0.04526	16.61
0.823	1.024	0.0403	20.95
0.6527	0.9116	0.03589	26.41
0.5176	0.8118	0.03196	33.31
0.4105	0.7229	0.02846	42
0.3255	0.6438	0.02535	52.96
0.2582	0.5733	0.02257	66.78
0.2047	0.5106	0.0201	84.21
0.1624	0.4547	0.0179	106.2
0.1288	0.4049	0.01594	133.9
0.1021	0.3606	0.0142	168.9
0.08098	0.3211	0.01264	212.9
0.06422	0.2859	0.01126	268.5
0.05093	0.2546	0.01003	338.5
0.04039	0.2268	0.008928	426.9
0.03203	0.2019	0.00795	538.3
0.0254	0.1798	0.00708	678.8
0.02014	0.1601	0.006305	856
0.01597	0.1426	0.005615	1,079
0.01267	0.127	0.005	1,361
0.01005	0.1131	0.004453	1,716
0.007967	0.1007	0.003965	2,164
0.006318	0.08969	0.003531	2,729
0.00501	0.07987	0.003145	3,441

44 of 44 sizes shown. Values are calculated from the AWG progression and rounded for display. Cable manufacturers may publish slightly different nominal values or resistance limits.

AWG, mm and mm² measure different things

AWG is a gauge number. Millimetres measure diameter, while square millimetres measure cross-sectional area. For a round conductor, area is π × diameter² ÷ 4. Doubling diameter gives four times the area.

Diameter (mm) = 0.127 × 92^((36 − AWG) ÷ 39)
Area (mm²) = π × diameter² ÷ 4
For the formula: 1/0 = 0, 2/0 = −1, 3/0 = −2, 4/0 = −3

12 AWG is about 2.053 mm in diameter and 3.309 mm² in area. A 3.5 mm² conductor is closest to 12 AWG by area, but 12 AWG has only about 3.309 mm². If you need at least 3.5 mm², the next listed size is 11 AWG at about 4.172 mm². Check availability and the cable specifications before substituting sizes.

Reference and calculation method

The AWG progression and annealed-copper resistance reference come from NBS Handbook 100, Copper Wire Tables. We calculate geometry from the progression instead of rounding intermediate diameters. For a manufacturer reference, see Victron’s AWG to metric chart.

Reading a real cable label

Can I measure the outside of an insulated wire?

The outside measurement includes insulation, so it cannot directly tell you conductor area. Use the manufacturer’s conductor specification. The diameter here is for a solid round conductor with the stated area.

Does the chart work for stranded cable?

Its area describes the total conducting metal. A stranded bundle has gaps and a different outside diameter, so this solid-round equivalent is not a measurement of the finished bundle. Use the cable datasheet for physical fit and maximum resistance.

Is 10 AWG the same as 6 mm²?

10 AWG is about 5.261 mm². A 6 mm² conductor has more area. They may appear near each other in reference tables, but they are not exact equivalents. Check electrical and mechanical requirements before substituting one for the other.

Does the gauge tell me the maximum current?

Gauge describes conductor size. Current capacity also depends on the material, insulation, temperature, bundling and installation. This chart does not assign a universal amp rating to a gauge. Use the wire-sizing tool to check voltage drop, then verify ampacity separately.