Electrical Cable Size [2021] Access

Always consult the latest edition of your local electrical code (NEC, CEC, IEC, BS 7671) as legal requirements supersede engineering approximations. Last reviewed: April 2026. This guide is for informational purposes. Always involve a licensed electrical engineer for critical installations.

For three-phase:

#1/0 AWG: 0.98 ohms/1000 ft → R = 0.29 ohms → VD = 5.8V (4.8%) – acceptable. electrical cable size

#6 AWG: 2.4 ohms/1000 ft → R = 0.72 ohms → VD = 14.4V (12%) – still high.

#10 AWG: 3.9 ohms/1000 ft → R = 2×150/1000×3.9 = 1.17 ohms → VD = 23.4V (19.5%) still too high. Always consult the latest edition of your local

[ A = \frac\sqrtI_sc^2 \times tk ]

[ R = \rho \fracLA ]

Using approximate method: #12 AWG (6.5 ohms/1000 ft) → R total = 2×150/1000×6.5 = 1.95 ohms. VD = 20×1.95 = 39V (32%!) → completely unacceptable.