AWG Wire Gauge Chart
American Wire Gauge diameters, inches and millimetres, with cross-sectional area in mm² for every standard size from AWG 40 to AWG 0. Values are derived from the exact AWG definition (ASTM B258).
| Gauge | Diameter (in) | Diameter (mm) | Area (mm²) |
|---|
Standard: ASTM B258 (AWG definition) · Data checked: 2026-10-14
Frequently asked questions
Why does a larger AWG number mean a thinner wire?
The gauge scale is a geometric progression that grew out of the number of drawing steps used to make the wire, not out of its size. As wire was drawn thinner it went through more passes, so the number went up. The numbers are now fixed by definition rather than by manufacturing.
Is AWG the same as SWG or BWG?
No, and they disagree. American Wire Gauge is the US standard; Standard Wire Gauge (SWG, formerly Imperial Wire Gauge) was the British one; Birmingham Wire Gauge is a third, used for tube and sheet. At the same gauge number they give different diameters — 10 AWG is 2.588 mm, while 10 SWG is 3.251 mm. If a drawing does not say which gauge system it uses, ask.
What is the actual formula behind the numbers?
Diameter in inches = 0.005 x 92^((36-n)/39), where n is the gauge number. AWG 36 is exactly 0.005 in and AWG 0000 is exactly 0.46 in. Successive sizes differ by the 39th root of 92, about 1.1229.
Can I use the diameter to work out current capacity?
Not on its own. Ampacity depends on the insulation temperature rating, ambient temperature, how many conductors share a raceway, and the applicable code, not just cross-sectional area. Use the cable ampacity table and derate it properly.