WIRE GAUGE CHARTS
4 wire in mm
Thickness: 5.19 mm diameter (0.204 inches), 21.15 mm² cross-section of solid copper.
Specifications
- Diameter
- 5.19 mm
- Diameter (imperial)
- 0.204 in
- Cross-section
- 21.15 mm²
- Area (kcmil)
- 41.7
- Copper resistance
- 0.248 Ω/1000 ft
- Copper resistance (metric)
- 0.82 Ω/km
- Copper weight
- 189.5 g/m
- Ampacity (NEC 75 °C)
- 85 A
Nearest metric sizes
21.15 mm² does not match a standard metric cable size exactly. The closest conventional cross-sections are10 mm², 16 mm² and 25 mm²— engineers round this wire up (larger cross-section) for ampacity, or accept the raw equality for signal work.
One gauge away:5 · thinner3 · thickerFull chart →
Frequently asked questions
Is 4 gauge wire thick or thin?
4 gauge wire is 5.19 mm in diameter. On the AWG scale a lower number means a thicker wire, so 4 AWG sits toward the thick end, where service and feeder wires live.
How many amps can 4 gauge wire carry?
NEC Table 310.16 rates 4 AWG copper at 85 A in the 75 °C column (see our amp chart for 60/75/90 °C ratings). Use the calculator to check voltage drop at your run length; long runs often force one size thicker.
What diameter is 4 wire in millimeters?
4 gauge wire is 5.19 mm (0.204 in) in diameter, with a solid-conductor cross-section of 21.15 mm².