AWG to mm²

About AWG to mm²

AWG to mm² turns an American Wire Gauge size into the cross-sectional area metric cable is sold by. Pick a gauge and you get its area in mm² and its conductor diameter in both millimetres and inches, alongside the full chart from 4/0 down to 40. Enter a metric size instead and it names the closest gauge — and says whether that size is thinner or thicker than the one you asked for, which is the part that matters when you are substituting.

Why the AWG numbers run backwards

AWG counts drawing operations, not size. Wire is pulled through progressively smaller dies, and the gauge number is roughly how many times it was drawn — so a higher number has been stretched thinner. That is why 4/0 is a cable you can barely bend and 40 is finer than a human hair.

The scale is geometric rather than linear, which is why it cannot be expressed as a simple conversion factor. It is pinned at two points by definition: 36 AWG is exactly 0.005 in and 4/0 is exactly 0.46 in, with 39 steps in between. Each step therefore multiplies the diameter by the 39th root of 92. Two rules of thumb fall out of that and are worth memorising — three gauge steps double the cross-section, and ten steps multiply it by about ten.

Substituting metric cable for an AWG size

Metric cable comes in preferred sizes — 1.5, 2.5, 4, 6, 10 mm² and up — and almost none of them land exactly on a gauge. 12 AWG is 3.31 mm², which sits between the 2.5 and 4 mm² you can actually buy, so a substitution is always a decision about which way to round.

Round up unless you have a reason not to. Going thinner raises resistance and lowers the current the run can carry safely, and the effect compounds over length. Going thicker costs money and makes terminations harder but is never unsafe on its own. Either way the deciding number is the current rating for your installation and insulation type, not the area alone — the area only tells you which sizes are worth checking.

Frequently asked questions

What is 12 AWG in mm²?

12 AWG is 3.31 mm², with a conductor diameter of 2.05 mm. The nearest metric cable sizes either side of it are 2.5 mm² and 4 mm².

Why does a lower AWG number mean thicker wire?

The number counts how many times the wire was drawn through a die to reach its size. More draws means more stretching and a thinner result, so the count rises as the wire gets finer.

Is AWG a diameter or a cross-section?

The standard defines diameter, and the cross-section is calculated from it. That distinction matters because area grows with the square of diameter — halving the diameter quarters the area, and the current a conductor carries follows the area.

Does this work for stranded wire?

The chart gives the equivalent solid conductor. A stranded wire of the same AWG has the same total copper cross-section, but a slightly larger overall diameter because of the gaps between strands — so use the mm² figure for current, and measure the real thing when you need it to fit through something.