AWG to mm² Converter
American Wire Gauge (AWG) and square millimetres (mm²) describe the same thing — how fat a conductor is — but the two systems are used in different countries, and datasheets mix them freely. This converter gives the cross-section area and diameter for every common AWG size, in both directions.
Reference: AWG area doubles roughly every 3 gauge numbers (a 3-AWG step ≈ ×2 area, a 6-AWG step ≈ ×4)
Worked example: 12 AWG = 3.31 mm², diameter 2.05 mm — the standard size for 20 A branch circuits in North America. Its metric neighbour, 4 mm², is slightly larger and is the size you will meet on European and Middle Eastern sites for similar work. Remember that a lower AWG number means a fatter wire: 4/0 is far larger than 14 AWG, which trips up every beginner once.
Area alone does not size a conductor — ampacity and voltage drop decide. Use the wire size calculator for the actual selection.
Frequently asked questions
Does a bigger AWG number mean a bigger wire?
No — AWG runs backwards. Higher numbers are thinner wires: 14 AWG is thin (2.08 mm²), 4/0 AWG is very thick (107.2 mm²). The system comes from how many times the wire was drawn through dies.
Can I substitute the nearest mm² size for an AWG size?
Usually yes if the mm² size is equal or larger — for example 4 mm² for 12 AWG (3.31 mm²). Going smaller reduces ampacity and increases voltage drop, so never substitute down.
Why do AWG sizes skip numbers?
The gauge steps are geometric, not linear: each 3-gauge step roughly doubles the area. That is why the jump from 12 to 10 AWG is a bigger change than from 12 to 13 would be.