28 AWG wire size
0.321 mm · 0.081 mm²
0.0126 in diameter · 212.904 Ω/km in copper
What 28 AWG is used for
USB data pairs and very fine internal wiring.
The numbers
| Diameter | 0.321 mm · 0.0126 in |
| Cross-sectional area | 0.081 mm² |
| Resistance, copper | 212.904 Ω/km · 64.893 Ω per 1,000 ft |
| Resistance, aluminium | 348.253 Ω/km |
| NEC 60 °C copper ampacity | — outside the common building-wire range |
How 28 compares
The gauge scale is geometric, so the useful comparisons are ratios rather than differences. 22 AWG is twice the diameter, which is four times the area.
| Gauge | Diameter | Area | Ω/km copper | vs 28 |
|---|---|---|---|---|
| 22 | 0.644 mm | 0.326 mm² | 52.96 | 4.02× the area |
| 24 | 0.511 mm | 0.205 mm² | 84.21 | 2.53× the area |
| 26 | 0.405 mm | 0.129 mm² | 133.9 | 1.59× the area |
| 30 | 0.255 mm | 0.051 mm² | 338.53 | 0.63× the area |
| 32 | 0.202 mm | 0.032 mm² | 538.28 | 0.4× the area |
| 34 | 0.16 mm | 0.02 mm² | 855.91 | 0.25× the area |
Frequently asked questions
What is 28 AWG in mm?
0.321 mm in diameter (0.0126 inches), with a cross-sectional area of 0.081 mm².
Is 28 AWG used for power wiring?
Not for building circuits. It is a signal and low-current gauge — thinner than anything a domestic branch circuit uses.
What is the resistance of 28 AWG copper?
212.904 Ω per kilometre, or 64.893 Ω per 1,000 feet, for annealed copper at 20 °C. The same gauge in aluminium is about 348.25 Ω/km — 1.64 times higher, which is why aluminium wiring is sized larger for the same load.
Why do smaller AWG numbers mean thicker wire?
The number counts drawing operations. Wire is pulled through progressively smaller dies, and the gauge records how many passes it took — so more passes means a higher number and a thinner wire.