Voltage drop calculator
Published On: 25/02/2026
Voltage Drop Calculator
Estimate voltage drop across a wire based on current, distance, and wire size. Supports DC / single-phase and a simple 3-phase option.
Inputs explained:
• System voltage: supply voltage (e.g., 12V DC, 120V, 230V).
• Current (A): load current in amps.
• One-way length: distance from source to load (the calculator applies a round-trip factor for DC/single-phase).
• Wire gauge / area: conductor size (AWG or mm²).
• Material: copper has lower resistance than aluminum.
Formula (simplified):
DC / 1φ: Vdrop = I × R_total, where R_total = R_per_m × (2 × length)
3φ: Vdrop ≈ √3 × I × R_per_m × length
• System voltage: supply voltage (e.g., 12V DC, 120V, 230V).
• Current (A): load current in amps.
• One-way length: distance from source to load (the calculator applies a round-trip factor for DC/single-phase).
• Wire gauge / area: conductor size (AWG or mm²).
• Material: copper has lower resistance than aluminum.
Formula (simplified):
DC / 1φ: Vdrop = I × R_total, where R_total = R_per_m × (2 × length)
3φ: Vdrop ≈ √3 × I × R_per_m × length
This uses typical copper/aluminum resistance at ~20°C (approx).
Safety note: This calculator is for estimation only. Always follow electrical code and manufacturer guidance for conductor sizing, insulation, and protection devices.
Voltage Drop Calculator — Description
The Voltage Drop Calculator estimates how much voltage is lost across a wire run based on current, distance, conductor size, and material (copper or aluminum). It returns the voltage drop in volts, the percentage drop, and the approximate voltage available at the load. This is useful for selecting wire gauge in DC systems, low-voltage installations, and basic AC power runs.
Results are approximate and intended for planning only. Real-world drops can vary with temperature, connections, and power factor.