They measure the same thing in two systems: AWG is a gauge number that gets smaller as the cable gets thicker, mm² is the conductor area directly. Conversion tables approximate, because the two systems rarely land on identical sizes.
Every cable on this shelf is sold under one of two systems, and mixing them is how an installation ends up a size under what it needed.
The two systems
Square millimetres state the cross-sectional area of the conductor. AWG assigns a number that decreases as the conductor grows, with each step a fixed ratio from the last. Neither is more accurate; they are simply different notations for the same physical quantity.
Why conversion is approximate
The standard sizes in each system do not coincide. A conversion table gives the nearest equivalent, which is usually slightly larger or slightly smaller, and rounding in the convenient direction is how a marginal cable gets chosen.
What actually governs the choice
Current, run length and acceptable voltage drop — and then the manufacturer’s rating for that cable in that installation method. A conductor bundled with others, or run through insulation, carries less than the same conductor in free air, and the rating tables account for that.
The mislabelling problem
Cable sold as a gauge it does not meet is a known issue in this market, and it is measurable: strip a sample and measure the conductor. Suppliers who publish a conductor area in mm² alongside the gauge are stating something checkable.
What people ask before they order
Is an AWG figure a conductor area?
It corresponds to one, but it is a gauge step rather than a measurement. Two adjacent gauge numbers differ by a fixed ratio, which is why the numbering runs backwards and why the steps are uneven in mm².
Does the insulation count?
No, and that is a common source of error when a cable is measured rather than read. The specification refers to the conductor, not the outside diameter.
Last reviewed 16 September 2026