AWG to mm Calculator

Convert any American Wire Gauge (AWG) size to diameter in mm and inches, area in mm² and kcmil.

⏱ Updated: 18 Sep 2026

Calculator

Free AWG to mm calculator: convert an American Wire Gauge size to diameter and cross-sectional area.

Accepts -3 to 40. The oversized gauges are numbered in reverse: 0000 AWG = -3, 000 AWG = -2, 00 AWG = -1, 0 AWG = 0.

Diameter
0 mm
Diameter
0 in
Cross-Sectional Area
0 mm²
Area
0 kcmil

Enter an AWG gauge number to get its diameter, cross-sectional area, and kcmil rating instantly.

How to Use the AWG to mm Calculator

Type an American Wire Gauge number into the single field — anything from -3 up through 40 — and the diameter, area, and kcmil figures update immediately. For the oversized gauges, remember 0000 AWG maps to -3, 000 to -2, 00 to -1, and 0 to 0.

American Wire Gauge isn't a lookup table dressed up as a formula — it's an actual geometric progression, defined by the standard itself, with a fixed ratio between one gauge and the next.

Diameter (mm) = 0.127 × 92^((36 − AWG) ÷ 39)

That 92^(1/39) ratio is the entire system in one number: each step down in gauge multiplies the diameter by roughly 1.123, and the standard is built so that going from 36 AWG to 0 AWG (36 steps) multiplies the diameter by exactly 92.

Here's the part that actually makes the system elegant rather than arbitrary: every 3-gauge step roughly doubles the cross-sectional area, because 92^(3/39) works out to almost exactly 2. Go from 10 AWG to 7 AWG and you've doubled the copper. That's not a coincidence — the standard's base was chosen specifically so area, which is what actually matters for current-carrying capacity, scales in clean powers of two across gauge steps, even though the numbers themselves look arbitrary at a glance.

It's also why AWG runs backwards from what people expect the first time they encounter it: a bigger number means a thinner wire, because the numbers are logarithmic, not linear. 40 AWG is hair-thin; 0000 AWG is the diameter of a pencil. Anyone expecting "higher number, more wire" gets tripped up here at least once.

Kcmil (thousand circular mils) shows up in the results because it's the standard unit for anything above 4/0 AWG in North American wire tables — past that size, electricians stop using AWG numbers entirely and switch to kcmil directly. Diameter in inches and area in mm² are just unit conversions of the same underlying number, useful depending on whether you're matching a wire to a metric datasheet or a spec quoted in mils.