WireSizing
Wire gauge reference & calculator

What Wire Size for 70 Amps?

Copper Wire
4 AWG
5.1894 mm · 21.1506 mm²
Aluminum Wire
3 AWG
5.8273 mm · 26.6705 mm²
Breaker: 70A · Based on NEC Table 310.16 (75°C insulation)

Common Uses for 70A Circuits

Large sub-panels, commercial equipment

4 AWG Copper — Key Specs

Diameter5.1894 mm (0.204307")
Area21.1506 mm²
Resistance at 20°C0.8151 Ω/km
Weight189.51 kg/km
Ampacity (75°C)70 A

Important: For long wire runs, you may need to upsize the wire to compensate for voltage drop. NEC recommends keeping voltage drop under 3% for branch circuits. Use our voltage drop calculator to check.

Related

4 AWG full specifications → Full AWG chart → Wire size calculator → Ampacity tables →