AWG to mm² Conversion and Ampacity Table

No AWG size equals a round metric number, so every conversion ends with a decision: round up to the next AWG size, never down.

The four sizes that dominate small installations convert as follows: 14 AWG is 2.08 mm², 12 AWG is 3.31 mm², 10 AWG is 5.26 mm² and 8 AWG is 8.37 mm². The steps are uneven — the jump from 12 to 10 AWG adds 1.95 mm², while 10 to 8 adds 3.11 mm² — which is why metric minimums so often land between two AWG numbers.

Ampacity under NEC 310.16 at 75 °C terminations climbs with the same steps: 15 A for 14 AWG, 20 A for 12 AWG, 30 A for 10 AWG and 40 A for 8 AWG. These are caps, not targets, and they assume the termination temperature rating stated.

Worked example one, the protective conductor: a metric minimum of 2.5 mm² lands between 14 AWG (2.08 mm²) and 12 AWG (3.31 mm²). Rounding down to 14 AWG leaves the installation about 17% short of the minimum — a compliance failure produced by arithmetic. The correct conversion is 12 AWG.

Worked example two, the live conductor: a 32 A breaker cannot be paired with 10 AWG, because 10 AWG is capped at 30 A. The live side of a 32 A circuit in AWG country is 8 AWG at 40 A — two full sizes above the size that the earth question alone would suggest.

Temperature sits underneath all of these numbers. Copper resistivity is 1.68 × 10⁻⁸ Ω·m at 20 °C and rises roughly 0.4% per °C, so a conductor measured at 60 °C reads about 16% higher than its 20 °C value; conversions fix the cross-section, but resistance in service is always the hotter number.

• 14 AWG = 2.08 mm², capped at 15 A
• 12 AWG = 3.31 mm², capped at 20 A
• 10 AWG = 5.26 mm², capped at 30 A
• 8 AWG = 8.37 mm², capped at 40 A

Further reading

• Earth Conductor Sizes by Breaker Rating
• RCD Ratings, Trip Times and Loop Impedance