AWG to mm² Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 10/11/2026
A cable's cross-section in mm² is calculated from its AWG gauge with diameter = 0.127 × 92^((36−AWG)/39), then cross-section = π × (diameter/2)². A 12 AWG cable, common in US home wiring, corresponds to about 3.31 mm².
Explanation
AWG (American Wire Gauge) is the wire-sizing system used in the United States and Canada, as opposed to the mm² cross-section used in Europe and most other countries. Unlike a linear scale, a smaller AWG number designates a thicker wire (hence a larger cross-section): a 10 AWG cable is thicker than a 14 AWG cable, and the thickest gauges carry special designations (00, 000, 0000, often written 2/0, 3/0, 4/0) rather than explicit negative numbers, even though the mathematical formula treats them exactly as such (-1, -2, -3). This scale follows a precise geometric progression, defined by the American ASTM B258 standard: each AWG gauge has a diameter 92^(1/39) times larger than the next gauge, a factor of about 1.1229 — which ensures that a 3-gauge AWG change corresponds roughly to doubling or halving the cross-section. This calculator converts an already-chosen AWG gauge (on an American wiring diagram, for example) into its mm² equivalent, the reference unit for choosing or comparing a cable under European standards. To directly determine the cross-section needed based on current, length, and allowed voltage drop for an installation, see instead our electrical cable cross-section calculator, which starts from the need rather than an already-known gauge.
Example: a 12 AWG cable
Inputs
Gauge: 12 AWG.
Calculation
Diameter = 0.127 × 92^((36−12)/39) = 0.127 × 92^0.6154 ≈ 2.0525 mm. Cross-section = π × (2.0525/2)² ≈ 3.3088 mm².
Result
A 12 AWG cable corresponds to a cross-section of about 3.31 mm², the closest commonly available size in Europe.
Frequently asked questions
Why does a smaller AWG number mean a thicker wire?
It's a convention inherited from the historical wire-drawing manufacturing process: the AWG number corresponds to the number of successive drawing steps needed to reach that diameter from a raw rod, each step reducing the diameter further. The more drawing steps (higher AWG number), the thinner the final wire; a thick wire, which needs fewer steps, therefore gets a smaller number.
What do the 00, 000, and 0000 gauges mean?
These are the thickest commonly used gauges on the AWG scale, beyond gauge 0: they correspond mathematically to the negative values -1, -2, and -3 in the conversion formula, and are often written 2/0, 3/0, and 4/0 in North American technical documentation, by convention rather than mathematical necessity.
Does this conversion give a standardized cable size in Europe?
Not necessarily exactly: standardized cable sizes in Europe (1.5 mm², 2.5 mm², 6 mm², etc.) follow their own scale of common values, which doesn't exactly match the cross-sections obtained by direct conversion from an AWG gauge. This calculator gives the mathematically equivalent cross-section; when buying cable in Europe, you then need to choose the next standard size up that's available, then check its electrical resistance for the cable length involved.