mm² to AWG

AWG = 36 − 39 × log₉₂(√(4 × mm² ÷ π) ÷ 0.127). The American wire gauge is a 92nd-root geometric series set in 1857, so inverting it takes a logarithm: 3.31 mm² is 12 AWG, and 2.08 mm² is 14 AWG.

European and Asian cable is sized in square millimeters — 1.5 mm² for lighting, 2.5 mm² for power circuits — and when that cable meets a US terminal, connector, or ampacity table, someone needs the AWG number: 2.5 mm² is closest to 13 AWG, 1.5 mm² to 15 AWG, 4 mm² to 11 AWG. This converter finds the exact AWG value and the nearest standard gauge.

By EnginStack Editorial Team | Reviewed against NIST, BIPM and primary-source documentation About →
mm²
— AWG
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Authority: NIST SP 811 (SI usage guide) and the 1959 International Yard and Pound Agreement. The coefficient above is a defined value — it does not come from measurement and carries no uncertainty.

mm² to AWG

The reverse of the AWG formula — AWG = 36 − 39·log92(d/0.127), with the diameter derived from the area as d = √(4A/π) — returns a continuous value. Since AWG only exists as integer steps, the practical result is the nearest standard gauge, which is what terminal compatibility actually needs: a 2.5 mm² conductor lands between 13 and 14 AWG, and the connector is chosen for the exact measured diameter, not the label. Imported equipment with metric terminations and US wire stock meet at this conversion daily.

AWG = 36 − 39 × log92( √(4A/π) / 0.127 )
2.5 mm² ≈ 13 AWG  ·  1.5 mm² ≈ 15 AWG  ·  4 mm² ≈ 11 AWG
The formula inverts the 1857 AWG definition exactly.

Worked Examples

Example 1: Match a 2.5 mm² European power circuit

√(4 × 2.5 / π) = 1.784 mm → 13 AWG

Example 2: Match a 1.5 mm² lighting circuit

√(4 × 1.5 / π) = 1.382 mm → 15 AWG

Example 3: Match a 4 mm² circuit

√(4 × 4 / π) = 2.257 mm → 11 AWG

Common mm² to AWG Values

mm²AWGContext
1.5 mm²—15 AWGEuropean lighting circuits.
2.5 mm²—13 AWGEuropean power circuits.
4 mm²—11 AWGLarge appliances.
6 mm²—9 AWGCooker and submain circuits.
10 mm²—7 AWGFeeders and EV chargers.

Engineering Context

mm²-to-AWG is the reverse of AWG to mm² and the same bridge from the metric side. The ampacity implications connect to watts to amps — a 2.5 mm² circuit is typically protected at 16–20 A in Europe — and the electric hub collects the full wire story.

The answer on this page is almost never an exact gauge, and that is the point to carry away. Metric conductor sizes do not land on the American wire gauge series, so 2.5 square millimeters converts to 13.2 AWG and is called 13 AWG for convenience; the nearest standard sizes are 12 and 14. A designer matching a metric cable to a US terminal, connector or ampacity table should therefore treat the result as a band and choose the larger conductor if the current is near a limit, never the smaller. Ampacity is also set by insulation temperature rating and installation method rather than by cross-section alone, which is why the same wire carries different current in the National Electrical Code and in IEC practice.

More: AWG to mm² · W to A · V to A · Electric Guide · Electric Hub · AWG Chart

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Frequently Asked Questions

What AWG is 2.5 mm² cable?

2.5 mm² is closest to 13 AWG (2.62 mm² area). It is the standard European power circuit cable, typically protected at 16–20 A.

What AWG is 1.5 mm² cable?

1.5 mm² is closest to 15 AWG (1.65 mm²). It is the standard European lighting circuit cable, protected at 10–16 A.

Is the AWG match exact?

The formula gives a continuous value, but AWG only exists as integer steps — so the result is the nearest standard gauge. For terminal fit, always use the measured diameter, not the rounded gauge label.