AWG Wire Gauge to mm & Area
AWG gauge to diameter in mm and inches, area in mm² and kcmil, and Ω/km for copper or aluminium — from the gauge law, or the nearest gauge for a size.
Diameter, area, kcmil and Ω/km · Ω/1000 ft for the gauge (solid or stranded), the exact fractional gauge for a diameter or area, and a table of neighbouring gauges.
Example: 12 AWG: 2.053 mm, 3.31 mm², 6.53 kcmil, 5.21 Ω/km copper at 20 °C. 4/0 is exactly 0.4600 in (11.68 mm, 211.6 kcmil). A 2.5 mm conductor is nearest 10 AWG (10.30).
A gauge law,
not a table.
The two fixed points behind AWG, how diameter, area and resistance follow, and what is deliberately not here.
The law
American Wire Gauge is defined by two diameters — 4/0 (0000) = 0.4600 in and No. 36 = 0.0050 in — with 39 gauge steps between them forming a geometric series. So d(in) = 0.005 × 92^((36 − n)/39): each step changes the diameter by about 12.3 %, each six steps double the area, and every three steps double the resistance. The aught sizes count 1/0 = 0, 2/0 = −1, 3/0 = −2, 4/0 = −3.
Area and resistance
Area is π d²/4 (kcmil is the diameter in mils squared ÷ 1000). Resistance per kilometre is ρ ÷ A × (1 + α(T − 20)) with the copper and aluminium resistivities from the site’s conductor data — the International Annealed Copper Standard from NBS Handbook 100 and 61 % IACS aluminium. Stranded conductors multiply the area by the strand count; their overall diameter is larger than a solid wire’s.
Not here
Ampacity depends on insulation, ambient, bundling and the code, and is not a property of the wire; the page does not give one. SWG, BWG and the sheet-metal gauges are lookup tables, not formulas, and are not embedded — the Sheet Metal Gauge page covers sheet. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- AWG gauge law d = 0.005 × 92^((36 − n)/39) in (4/0 = 0.4600 in, No. 36 = 0.0050 in, 39 steps); copper 0.017241 and aluminium 0.028264 Ω·mm²/m (NBS Handbook 100 / 61 % IACS)
Last reviewed 21 September 2026. How results are checked: How we verify.