Code Comparison Cable Sizing
mm² and AWG are not simply two labels for the same underlying sizes — direct conversion without checking real standard sizes is a common mistake.
PEC and AS/NZS use metric mm² cross-sections; the NEC uses AWG transitioning to kcmil. It's tempting to treat this as a simple unit conversion — it isn't, because the two systems don't share the same set of standard, commercially manufactured sizes.
Converting a metric cross-section to its closest circular-mil equivalent gives you a number, but that number often doesn't land exactly on a standard AWG size — it falls between two standard sizes. Rounding up or down introduces exactly the kind of ambiguity that a proper code-specific calculation avoids entirely.
Run the actual design current and conditions through the applicable code's own calculator, rather than sizing under one code and converting the result to another code's units. A 25mm² PEC result isn't reliably "the same as" a specific AWG size under the NEC — it's a completely independent calculation that happens to produce a broadly similar physical conductor.
Multinational projects sometimes require documentation in both systems — in that case, run the calculation twice, once under each code, rather than converting one result into the other's units after the fact.
Engr. Jason Morales — Founder, SolarEnergyPH & OhmWorks