Wire Gauge Converter (AWG ↔ mm² ↔ SWG)
Convert
Wire gauge systems are confusingly inverse — higher AWG numbers mean THINNER wire (AWG 30 is hair-thin, AWG 0000 is finger-thick), and the system is logarithmic: each three-gauge step roughly doubles the cross-section area. The conversion uses the standard formula d(mm) = 0.127 × 92^((36−AWG)/39), which gives the geometric progression between 36 AWG (0.127 mm) and 0000 AWG (11.68 mm). Cross-section is computed as π(d/2)² in mm² and (d_in × 1000)² in circular mils (kcmil). Resistance per length uses copper resistivity ρ = 17.241 nΩ⋅m at 20°C (aluminum 28.264 nΩ⋅m). Ampacity tables come from the NEC: 'chassis wiring' is single-wire, free-air (max ~75°C insulation) and 'power transmission' is the much more conservative bundled-cable rating. British SWG is reported as the nearest match — it's a tabulated standard, not a formula.
| AWG | mm | mm² | Ω/km Cu | A (power) |
|---|---|---|---|---|
| 0 | 8.251 | 53.475 | 0.32 | 150 |
| 2 | 6.544 | 33.631 | 0.51 | 94 |
| 4 | 5.189 | 21.151 | 0.82 | 60 |
| 6 | 4.115 | 13.302 | 1.30 | 37 |
| 8 | 3.264 | 8.366 | 2.06 | 24 |
| 10 | 2.588 | 5.261 | 3.28 | 15 |
| 12 | 2.053 | 3.309 | 5.21 | 9.3 |
| 14 | 1.628 | 2.081 | 8.29 | 5.9 |
| 16 | 1.291 | 1.309 | 13.17 | 3.7 |
| 18 | 1.024 | 0.823 | 20.95 | 2.3 |
| 20 | 0.812 | 0.518 | 33.31 | 1.5 |
| 22 | 0.644 | 0.326 | 52.96 | 0.92 |
| 24 | 0.511 | 0.205 | 84.21 | 0.577 |
| 26 | 0.405 | 0.129 | 133.90 | 0.361 |
| 28 | 0.321 | 0.081 | 212.92 | 0.226 |
| 30 | 0.255 | 0.051 | 338.55 | 0.142 |
AWG diameter from d = 0.127 × 92^((36−n)/39). Resistance uses ρ(Cu) = 17.241 nΩ·m, ρ(Al) = 28.264 nΩ·m at 20°C. Ampacity values are conservative reference figures — always check your jurisdiction's wiring code for actual installations.
How to use
- Pick what you know — AWG number, wire diameter in mm, or cross-section area in mm².
- Switch material between Copper and Aluminum to update resistance per length.
- Read the equivalent SWG, kcmil, and the two ampacity ratings (chassis = single wire in free air, power = bundled cable).
- Or click any row in the reference table at the bottom to jump straight to that AWG.
Frequently asked questions
- Why are larger AWG numbers smaller wires?
- Historical accident — AWG numbers originally counted the number of drawing-die passes used to manufacture the wire. Each pass through a smaller die thinned the wire further, so '36 passes' (36 AWG) gave the thinnest practical wire. For wires thicker than 1 AWG, the numbering reverses to 0, 00, 000, 0000 (also written 1/0 to 4/0).
- Which ampacity should I actually use for my project?
- Neither without checking your jurisdiction's code. The 'chassis wiring' column is roughly NEC table 310.15 for single-conductor, free-air, ~75°C insulation — fine for short internal wiring in an electronics chassis. The 'power transmission' column matches conservative ratings for bundled, in-wall use with 60°C insulation and a 1.5–2× safety derating. For real installations always consult NEC, IEC 60364, or your national wiring code with the right insulation, ambient temperature, and bundling corrections.
- Why doesn't SWG match AWG?
- SWG is a separate British system, defined as a hand-tabulated list rather than a formula, last codified in 1884. The conversion shown is the nearest SWG to the actual diameter — they rarely match an AWG number exactly. Modern wire is almost always sold by AWG or mm², except in some legacy UK / Commonwealth contexts.
- What's a 'circular mil'?
- A circular mil is the area of a circle one mil (0.001 in) in diameter — i.e. π/4 × (0.001 in)² ≈ 506.7 µm². It's used because for round wire it's literally the diameter-in-mils squared, eliminating the π factor. kcmil = 1000 circular mils. Common for North American power transmission lines.
Related tools
CSS Unit Converter
Convert between px, rem, em, pt, vw, vh, and % using your own base font size and viewport.
JSON ↔ YAML Converter
Convert JSON to YAML or YAML to JSON — pick the indent and copy the result.
Data Size Converter
Convert between bytes, KB, MB, GB, TB — in decimal (1000) or binary (1024).
Roman Numeral Converter
Convert between Arabic numbers and Roman numerals from 1 to 3999.
Number Base Converter
Convert numbers between binary, octal, decimal, and hexadecimal.
Unit Converter
Convert length, weight, temperature, area, volume, speed, and time.