AWG, kcmil and Square Millimeter Size Chart

AWG diameter and area

This is a simultaneous lookup chart, not a wire-sizing result. AWG describes a nominal conductor size. A smaller ordinary gauge number represents a larger conductor; 1/0 through 4/0 continue above 1 AWG.

Diameter is the nominal round bare-wire equivalent. It is not the outside diameter of an insulated or stranded cable. Areas are nominal geometry, rounded for display, following the AWG relationship documented in NBS/NIST Copper Wire Tables.

kcmil area table

One kcmil is one thousand circular mils. A circular mil is the area of a circle one mil (0.001 inch) in diameter; it is not one square mil. The area conversion is approximately 0.5067075 mm² per kcmil.

Use the size comparison correctly

• A numerical area conversion is not a replacement-size approval. AWG and metric products can have different standard nominal sizes, stranding, listings, and terminal suitability.
• A 12 AWG conductor’s area is about 3.31 mm². That does not turn a 2.5 mm² or 4 mm² product into the same listed conductor.
• Use the actual manufacturer outside diameter for conduit fill, bend radius, or cable routing. Bare-equivalent diameter excludes insulation and construction differences.
• Ampacity also depends on material, insulation, terminals, ambient conditions, conductor count, wiring method, and the applicable rules. This chart intentionally has no “maximum amps” column.

For a single conversion use the existing unit converter. For conductor selection conditions use the ampacity tool and read the cable-marking reference.

For a separate circuit-performance estimate, use the voltage-drop calculator with the circuit length, load, material and size required by that tool. A nominal area lookup alone does not determine voltage drop.

Sources

• National Bureau of Standards / NIST: Copper Wire Tables, Handbook 100 (1966): AWG geometry and conductor area