AWG to mm² Converter — Full Wire Size Chart | WireStandard

The AWG to mm² converter helps engineers and electricians cross-reference American Wire Gauge numbers with metric cross-sectional areas. Enter any AWG from 40 (thinnest) to 4/0 (thickest); the tool outputs diameter (mm), area (mm²), and rated ampacity. Essential for projects that mix NEC (USA) documentation with IEC 60364, BS 7671, or AS/NZS 3000 equipment specs.

Formula

AWG diameter: d(mm) = 0.127 × 92^((36−n)/39), where n is the AWG number (AWG 36 = 0.127 mm; AWG 0/1/0 = 8.252 mm). Area: A(mm²) = π × (d/2)². Sizes larger than AWG 1/0 are named 2/0, 3/0, 4/0 (n = −1, −2, −3 in the formula). AWG numbers decrease as conductor cross-section increases.

Worked Example

AWG 12: d = 0.127 × 92^(24/39) = 2.053 mm; A = π × 1.0265² = 3.31 mm². Nearest IEC standard size is 2.5 mm² (smaller — do not substitute). For full NEC ampacity equivalence under IEC or BS ratings, select 4 mm². Reverse: IEC 10 mm² ≈ AWG 8 (actual 8.37 mm²). Always round up to the next standard size — rounding down may reduce ampacity below the required rating.

Frequently Asked Questions

Why does AWG numbering go backwards — smaller number means larger wire?

AWG originates from the number of drawing-die passes required to reduce a rod to a given diameter. A wire drawn through 12 dies is thicker than one drawn through 24 dies. AWG 4/0 (four-aught) passes through the fewest dies and is the thickest size in common use. The numbering convention predates metric standards and remains in use in North American codes.

Can I just pick the nearest metric size by area?

Not directly. NEC Table 310.16 ampacity ratings are assigned to AWG sizes under specific insulation and installation conditions; IEC 60364-5-52 assigns ampacity to mm² sizes under different reference installation methods. An area-equivalent metric cable may carry a different rated current than the AWG wire it replaces. Use this calculator's full output — recommended AWG and recommended mm² — rather than converting area alone.

What about MCM or kcmil for large conductors?

Above 4/0 AWG (107 mm²), North American practice switches to kcmil (thousand circular mils). One circular mil = the area of a circle with 0.001-inch diameter; 1 kcmil = 0.5067 mm². Common sizes: 250 kcmil ≈ 127 mm², 350 kcmil ≈ 177 mm², 500 kcmil ≈ 253 mm². IEC equivalents at these sizes are 120, 150, and 240 mm² (standard preferred sizes from IEC 60228).