Wire Gauge Converter
Convert AWG wire gauge to diameter in mm and inches with cross-sectional area.
Includes ampacity ratings for copper and aluminum wire in free air and conduit.
Type in any field — the others update instantly. Enter AWG as a number (use -1 for 1/0, -2 for 2/0, -3 for 3/0, -4 for 4/0).
AWG (American Wire Gauge) is the standard wire size system in the US. Larger gauge numbers mean thinner wire.
AWG formula:
- Diameter (inches) = 0.005 × 92^((36 − AWG) / 39)
- Diameter (mm) = diameter (inches) × 25.4
- Area (mm²) = π × (diameter_mm / 2)²
Common AWG sizes:
| AWG | Diameter (mm) | Diameter (in) | Area (mm²) | Typical Use |
|---|---|---|---|---|
| 0000 (4/0) | 11.684 | 0.4600 | 107.22 | Service entrance |
| 0 (1/0) | 8.251 | 0.3249 | 53.49 | Service entrance |
| 4 | 5.189 | 0.2043 | 21.15 | Range/oven feeder |
| 10 | 2.588 | 0.1019 | 5.26 | Dryer, AC circuits |
| 12 | 2.053 | 0.0808 | 3.31 | General household 20A |
| 14 | 1.628 | 0.0641 | 2.08 | General household 15A |
| 18 | 1.024 | 0.0403 | 0.82 | Low-voltage, bells |
| 22 | 0.644 | 0.0253 | 0.33 | Electronics, signals |
Metric vs Imperial:
- In the US, wire is specified by AWG number
- In Europe and most other countries, wire is specified by cross-sectional area in mm²
- Common metric sizes: 0.5, 0.75, 1.0, 1.5, 2.5, 4.0, 6.0, 10, 16, 25 mm²
Why the numbers run backwards
The scale is a leftover from how wire was actually made. Drawing wire means pulling it through a die to make it thinner, then through a smaller die, and again. The gauge number counts the passes. More passes, thinner wire, higher number. That is the whole explanation, and once you know it the scale stops feeling arbitrary.
It also explains the odd formula above. Each pass reduces the diameter by a constant ratio rather than a constant amount, so the scale is geometric, not linear. The ratio works out at the 39th root of 92, about 1.123 per step. Which gives two shortcuts worth memorising:
- Three gauges roughly doubles or halves the cross-sectional area. 14 AWG is about twice the copper of 17, and half of 11.
- Six gauges doubles or halves the diameter.
- Ten gauges is a factor of about ten in area. 10 AWG has roughly ten times the copper of 20 AWG.
Below 1 AWG the numbering runs out of room and goes to 0, 00, 000 and 0000, written 1/0 through 4/0 and spoken “one aught” to “four aught”. Anything thicker than 4/0 is sized in thousands of circular mils (kcmil) instead, which is where utility and industrial conductors live.
A conversion caution: there is no exact AWG equivalent for a metric size, and vendors round in whichever direction suits them. 2.5 mm² sits between 14 AWG (2.08) and 12 AWG (3.31), closer to 13 which nobody stocks. If you are substituting one for the other on a real circuit, always round toward the thicker conductor and check the ampacity table for the standard you are working to, because IEC and NEC do not agree on how much current a given area may carry.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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