[ VD = \sqrt3 \times K \times I \times L / A ]
[ VD = 2 \times K \times I \times L / A ] electrical cable size
Introduction Selecting the correct electrical cable size is one of the most critical decisions in any electrical installation—whether it’s a low-voltage automotive circuit, a residential feeder, or a high-voltage industrial distribution network. An undersized cable overheats, destroys insulation, causes fires, and creates excessive voltage drop. An oversized cable wastes material, increases cost, adds unnecessary weight, and may be difficult to terminate. [ VD = \sqrt3 \times K \times I
[ A = \frac\sqrtI_sc^2 \times tk ]
#2 AWG: 1.54 ohms/1000 ft → R = 0.46 ohms → VD = 9.2V (7.7%) – getting close. [ A = \frac\sqrtI_sc^2 \times tk ] #2 AWG: 1
[ R = \rho \fracLA ]
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.