Cable Voltage Drop

Estimate conductor losses and the voltage available at the load.

Formulas

A(AWG) = π / 4 × [0.127 × 92^((36 − AWG) / 39)]² mm²

R = ρ × Leffective / (A × Nparallel); Leffective = L or 2L

ρCu = 0.017241 Ω·mm²/m; ρAl = 0.028264 Ω·mm²/m (20°C)

Vdrop = I × R; Vload = Vsupply − Vdrop; Ploss = I² × R

Drop = Vdrop / Vsupply × 100%; efficiency = Vload / Vsupply × 100%

DC resistance only at 20°C; no ampacity, insulation, connector, temperature rise, or AC impedance assessment.

Status thresholds are design heuristics: up to 3% low drop, over 3–5% review, over 5% high drop. They are not electrical-code compliance limits.