About

Electrical safety relies on the correct wire cross-sectional area to handle current loads without overheating. A frequent challenge for engineers outside the US is converting American Wire Gauge (AWG) or Circular Mils (cmil) into the metric standard: Square Millimeters (mm²).

Unlike simple area conversions, AWG is a logarithmic step system where a decrease in gauge number represents an increase in wire thickness. This tool provides precise mathematical conversions for arbitrary values and exact standard table lookups for industry-standard wire sizes, ensuring compliance with IEC and NEC cross-reference charts.

Formulas

For standard units, the conversion is linear. For AWG, it follows a logarithmic progression.

1 sq in = 645.16 mm²

For American Wire Gauge (n):

Area_mm² = 0.127² × 92^{36 - n19.5} × π4 × 10⁶

1 kcmil = 0.5067 mm²

Reference Data

AWG / kcmil	Area (mm²)	Approx Ampacity (Cu, 75°C)
18 AWG	0.823	14 A
16 AWG	1.31	18 A
14 AWG	2.08	20 A
12 AWG	3.31	25 A
10 AWG	5.26	35 A
8 AWG	8.37	50 A
6 AWG	13.30	65 A
4 AWG	21.15	85 A
2 AWG	33.62	115 A
1/0 AWG	53.49	150 A
4/0 AWG	107.22	230 A
250 kcmil	126.68	255 A

Frequently Asked Questions

This calculator determines the *cross-sectional area of the conductive material*. For stranded wire, the physical diameter is larger due to air gaps, but the electrical cross-section (mm²) remains roughly the same as the solid equivalent.

In the math formula, 0 AWG is n=0, 00 AWG is n=-1, 000 is n=-2, and 0000 is n=-3. This tool handles these inputs automatically via the dropdown selector.

The Reference Table provides *approximate* ampacities for copper at 75°C. However, real-world ampacity depends on insulation type (THHN, XHHW), ambient temperature, and conduit fill. Always consult NEC Table 310.15(B)(16) or local codes.

A circular mil is the area of a circle with a diameter of one mil (1/1000th of an inch). It is used for very large cables. 1 kcmil = 1000 cmil.