Voltage Drop Calculator

Cable voltage drop and percentage drop from the current, one-way run length, conductor cross-section and material — for DC / single-phase and three-phase circuits.

Circuit

Current A

One-way run length m

Conductor cross-section mm²

Conductor material

System

System voltage V

Used only to express the drop as a %.

Results

Voltage drop—

Percentage drop—

Voltage at load—

Loop resistance—

Vdrop = k × I × ρ × L / A, k = 2 for DC/single-phase (go & return) or √3 for three-phase; ρ ≈ 0.0175 Ω·mm²/m (copper), 0.0282 (aluminium) at ~20°C. Many codes limit drop to ~3–5%. This ignores temperature rise and reactance — adequate for sizing, not a substitute for code tables.