DC Voltage Drop Calculator

How This Calculator Works

Voltage drop occurs in all electrical cables due to the resistance of the conductor material. For DC systems, this is calculated using:

V_drop = (2 × L × I × ρ) / A

Where: L = cable length (one way, metres), I = current (Amps), ρ = resistivity of copper (0.0175 Ω·mm²/m), A = cable cross-section area (mm²)

The factor of 2 accounts for the return path (positive and negative cables).

Acceptable Voltage Drop

• Under 3% — Acceptable for most installations
• 3% to 5% — Marginal, may cause issues with sensitive equipment
• Over 5% — Unacceptable, will cause performance issues and potential damage

For inverters and chargers, keeping voltage drop below 3% is strongly recommended to ensure optimal performance and to avoid low-voltage alarms.