AWG to mm Calculator
Convert American Wire Gauge to millimetres, inches and cross-sectional area — or go the other way and find which AWG a given diameter corresponds to. Values come from the exact AWG definition, the same formula behind the tabulated ASTM B258 figures.
Cross-sectional area: — mm²
How the conversion works
The AWG system is defined by a geometric progression, not by a lookup table. The diameter of gauge number n in inches is:
Two fixed points anchor the scale: AWG 36 is exactly 0.005 in, and AWG 0000 (four aught) is exactly 0.46 in. The ratio between successive sizes is the 39th root of 92, which is roughly 1.1229 — so stepping one gauge changes the diameter by about 12.3%, and the cross-sectional area by about 26%. Multiplied by 25.4 to get millimetres, and the area follows from the circle formula A = π/4 × d².
This is the same definition that produces the published ASTM B258 tables, which is why the numbers here match those tables exactly rather than approximately.
Selected values
| Gauge | Diameter (mm) | Area (mm²) |
|---|---|---|
| AWG 0 | 8.2515 | 53.4751 |
| AWG 2 | 6.5437 | 33.6308 |
| AWG 4 | 5.1894 | 21.1506 |
| AWG 6 | 4.1154 | 13.3018 |
| AWG 8 | 3.2636 | 8.3656 |
| AWG 10 | 2.5882 | 5.2612 |
| AWG 12 | 2.0525 | 3.3088 |
| AWG 14 | 1.6277 | 2.0809 |
| AWG 16 | 1.2908 | 1.3087 |
| AWG 18 | 1.0237 | 0.8230 |
| AWG 20 | 0.8118 | 0.5176 |
| AWG 22 | 0.6438 | 0.3255 |
| AWG 24 | 0.5106 | 0.2047 |
| AWG 26 | 0.4049 | 0.1288 |
| AWG 28 | 0.3211 | 0.0810 |
| AWG 30 | 0.2546 | 0.0509 |
Standard: ASTM B258 (AWG definition) · Data checked: 2026-10-14
Things worth knowing
- The gauge runs backwards. A larger AWG number is a thinner wire. AWG 10 is thicker than AWG 20.
- Area is what matters for current. Going up three gauge steps roughly halves the cross-sectional area, which is why ampacity tables step in threes.
- This gives strand diameter, not cable diameter. A stranded conductor of a given AWG has the same total copper area but a larger overall diameter once insulation and the stranding lay are considered.
- It is a pure size conversion. How much current a wire can carry depends on insulation temperature rating, ambient temperature, how many conductors share a raceway and the applicable code — that is a separate question, and the ampacity table is the place to start.
- Metric wire uses mm² directly. Outside North America, conductors are usually specified by area (1.5 mm², 2.5 mm²) rather than by gauge.