AWG to mm² Conversion Chart, with the Next IEC Size Up

AWG to mm²

Diameters and areas follow the AWG formula of ASTM B258. Stranded wire of the same AWG has about the same copper area.

Larger sizes in kcmil

Above 4/0, North American sizes are given in thousands of circular mils: kcmil, formerly MCM. One kcmil is 0.5067 mm².

mm² to AWG

Building wire is rarely stocked in 17, 15, 13, 11, 9, 7 or 5 AWG, so this table skips those sizes.

Why the two series do not match

An AWG size is defined by the diameter of a solid wire, so its area is exact. An IEC 60228 size is nominal: a conductor passes if its resistance is at or below the limit for that size. A 2.5 mm² class 1 or class 2 copper conductor, for example, may have at most 7.41 Ω/km at 20 °C.

So never swap to a smaller size. 14 AWG is often listed as the equivalent of 2.5 mm², but it has only 2.08 mm² of copper, about 17% less. The other way round, 2.5 mm² can replace 14 AWG as far as cross-section goes.

Cross-section is only the first check. The current rating, the voltage drop over the run and the insulation rating must also meet the local wiring rules. US THHN wire, for instance, is rated 600 V, while IEC 60227 building wire is rated 450/750 V.