21 AWG (American Wire Gauge) wire specifications: 0.7229 mm diameter, 0.4105 mm² area. Resistance, weight, and common uses.
| Diameter | 0.7229 mm · 0.028462" · 28.46 mils |
| Cross-sectional area | 0.4105 mm² · 810 circular mils |
| Resistance (copper, 20°C) | 41.9985 Ω/km · 12.8011 Ω/1000ft |
| Resistance (aluminum, 20°C) | 68.8502 Ω/km · 20.9855 Ω/1000ft |
| Ampacity — copper 60°C | — A |
| Ampacity — copper 75°C | — A |
| Ampacity — copper 90°C | — A |
| Ampacity — aluminum 75°C | — A |
| Weight (copper) | 3.678 kg/km · 2.471 lbs/1000ft |
| Weight (aluminum) | 1.108 kg/km · 0.745 lbs/1000ft |
| Closest IEC 60228 size | 0.5 mm² |
| Skin depth at 60 Hz | 8.531 mm |
| Type | Temperature | Description |
|---|---|---|
| PVC | 60-105°C | General purpose insulation |
| Teflon (PTFE) | 200°C | High temperature applications |
| Silicone | 200°C | Flexible, high temperature |
| Enamel | 155-220°C | Magnet wire coating |
21 AWG wire (0.7229 mm diameter, 0.4105 mm²) is found in telephone wiring, intercom cables, and small signal wires in electronic equipment. It is also used in relay coils, small solenoids, and some types of hookup wire for prototyping and test equipment.
No. At 0.7229 mm diameter (0.4105 mm²), 21 AWG wire can safely carry only about 1–2 A continuously. NEC requires 14 AWG minimum for any branch circuit. Using 21 AWG on a 15 A or 20 A circuit would cause the wire to overheat immediately. It is limited to signal-level applications such as telephone wiring, intercoms, and low-power electronic circuits.