AWG wire gauge calculator (AWG ↔ mm²)

Diameter, cross-section and copper resistance for any AWG size from 0000 to 40, and the AWG size for a metric cross-section or a measured diameter. Results update as you type. All values are worked out from the definition of the gauge, not copied from a table.

Indicative calculation; verify before use.

AWG → metric

Gauge

Diameter (solid conductor)

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Diameter: –
Cross-section: –
Circular mils: –

Copper resistance at 20 °C

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Per 1000 ft: –
Nearest IEC 60228 size: –
Next IEC size up: –

mm² → AWG

Cross-section

mm²

IEC 60228 sizes (mm²):

Nearest AWG

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Exact gauge: –
Thinnest AWG at least as thick: –

This cross-section

Diameter (solid): –
Copper, 20 °C: –
Per 1000 ft: –

Measured diameter → AWG

Diameter of the bare conductor

Measure the bare copper with a micrometer or calliper, without the insulation or enamel.

Nearest AWG

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Exact gauge: –
Cross-section: –

Copper resistance at 20 °C

Per km: –
Per 1000 ft: –

Why there are no current (ampacity) ratings here

How much current a wire may carry is not a property of the gauge alone. It is set by the wiring rules that apply where you are (for example the NEC in the US or IEC 60364-5-52 in Europe) and depends on the insulation's temperature rating, the ambient temperature, how many conductors are bundled together and how the cable is installed. One number per gauge would be wrong for most uses, so this page gives none. Look up the table in the standard that applies to your installation.

For the same reason, an AWG size and a metric size with a similar cross-section are not automatically interchangeable in an installation. The IEC 60228 size shown is only the nearest nominal size.

How it works

d(n) = 0.127 mm × 92^((36 − n) / 39) n = AWG number; 0 = 1/0, 00 = −1, 000 = −2, 0000 = −3 A = π/4 × d² cross-section of a solid round conductor n = 36 − 39 × log(d / 0.127 mm) / log(92) gauge for a diameter R = ρ / A, ρ = 1.724 × 10⁻⁸ Ω·m copper at 20 °C (annealed copper standard, IACS 100 %) 1 in = 25.4 mm, 1 ft = 0.3048 m, circular mils = (d in mil)², 1 mil = 0.001 in

American Wire Gauge is defined by two fixed points: AWG 36 is 0.005 inch (0.127 mm) and AWG 0000 is 0.46 inch (11.684 mm), with 39 equal steps between them. Each step makes the diameter 92^(1/39) ≈ 1.1229 times larger, so six gauges double the diameter and three gauges roughly double the cross-section. Larger gauge numbers are thinner wires.

The resistance is for solid copper at 20 °C. Copper's resistance rises by about 0.4 % per °C. Stranded wire of the same gauge has a slightly larger overall diameter and slightly higher resistance than the solid figures here. Copper-clad aluminium or steel wire has a much higher resistance.

Worked example: AWG 14. d = 0.127 × 92^(22/39) = 0.127 × 12.82 = 1.628 mm (0.0641 in). A = π/4 × 1.628² = 2.081 mm². R = 1.724 × 10⁻⁸ / 2.081 × 10⁻⁶ = 8.285 Ω/km, or 8.285 × 0.3048 = 2.525 Ω/1000 ft. The nearest IEC 60228 size is 2.5 mm² (20 % larger).

Sources (checked 2026-11-03):

AWG definition (ASTM B258), d = 0.127 mm × 92^((36 − n)/39), AWG 36 = 0.005 in and AWG 0000 = 0.46 in: https://en.wikipedia.org/wiki/American_wire_gauge
Annealed copper standard, 58 × 10⁶ S/m at 20 °C (1 / 58 × 10⁶ = 1.724 × 10⁻⁸ Ω·m): https://en.wikipedia.org/wiki/International_Annealed_Copper_Standard
IEC 60228 nominal conductor cross-sections (0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50 mm² and larger): https://en.wikipedia.org/wiki/IEC_60228

We have not read ASTM B258 or IEC 60228 themselves; they are paid standards. IEC 60228 defines each size by a maximum conductor resistance, not an exact area, and lists sizes above 50 mm² that are not used here.