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AWG to mm²: Understanding Wire Gauge Sizing

Wire is sized two very different ways depending on where you are — here is how AWG and mm² relate to each other.

What AWG is

American Wire Gauge (AWG) is a standardized system used mainly in North America where, confusingly, a larger number means a thinner wire — 14 AWG is thinner than 10 AWG. It comes from a historical system based on how many times wire was pulled through progressively smaller dies.

What mm² is

Most of the rest of the world, following IEC standards, sizes wire by its actual cross-sectional area in square millimeters (mm²). A bigger number simply means a physically bigger wire, which many people find more intuitive than AWG.

Not a simple linear conversion

Because AWG numbering runs backwards, converting between the two is not a simple linear formula — it follows a logarithmic scale, so you generally need a lookup table or calculator rather than mental math.

Common sizes side by side

For household wiring, US 14 AWG and 12 AWG (common for lighting and outlet circuits) roughly correspond to 2.1 mm² and 3.3 mm², which sit close to — but not exactly on — the common European 1.5 mm² and 2.5 mm² sizes.

Why the size is a safety spec

Wire gauge determines how much current a wire can safely carry (its ampacity) and how much voltage it loses over distance. Undersized wire for a given load can overheat, so gauge is a safety spec, not just a technical detail.

Treat conversions as approximate

Because AWG and mm² sizes rarely align exactly, treat conversions as close approximations for reference, not exact substitutes — especially for anything load-bearing or safety-critical, where you should match a wire to the rating actually required by local electrical code.

Why AWG numbers run backwards

AWG traces back to a manufacturing process where wire was repeatedly pulled through a series of dies to make it thinner; the gauge number originally reflected how many drawing steps a wire had gone through, so a higher number meant more steps and a thinner result. That legacy is why AWG still counts up as wire gets thinner, unlike the metric mm² system, which simply measures physical area.

When the difference actually matters

For most everyday purposes — comparing an imported cable's spec sheet to a local one, for example — an approximate AWG-to-mm² conversion is good enough. For anything connected to mains power, motors, or other loads where undersized wire is a fire risk, always size wire using the ampacity tables and standards that apply in your country, not a rough conversion.

Frequently Asked Questions

Can I just use the closest AWG-to-mm² match for wiring a device?

For low-power signal wiring, a close approximation is usually fine. For anything carrying meaningful current — appliances, outlets, motors — match the wire to the ampacity rating specified by your local electrical code or the equipment manufacturer, rather than relying on an approximate size conversion.

Why don't AWG and mm² sizes round to clean numbers?

AWG follows a geometric progression based on wire-drawing history, while mm² is a straightforward area measurement. The two systems were never designed to align, so conversions land on numbers like 2.08 mm² instead of a clean 2.0 or 2.5.