How to reduce voltage drop?

Use larger wire gauge, shorten cable runs, increase voltage, or reduce current load. Keeping voltage drop under 3% for branch circuits is recommended.

What wire gauge should I use?

Wire gauge depends on current, distance, and acceptable voltage drop. Use this calculator to find the optimal gauge for your specific installation requirements.

Voltage Drop Calculator

Calculate voltage drop across electrical wiring to ensure safe and efficient power delivery.

Source Voltage (V)

Current (Amps)

Wire Length (meters, one way)

Wire Gauge (mm²)

Wire Material

Phase

What is Voltage Drop?

Voltage drop is the decrease in electrical potential as current flows through a wire. All conductors have resistance, which causes some voltage to be "lost" as heat. Excessive voltage drop can cause equipment malfunction, dim lights, and wasted energy.

Voltage Drop Formula

VD = (2 × ρ × L × I) / A

VD = Voltage drop · ρ = Resistivity (Ω·mm²/m) · L = One-way length (m) · I = Current (A) · A = Cross-section area (mm²)

For three-phase systems, the factor 2 is replaced by √3 (1.732).

Acceptable Voltage Drop

NEC (US) standard: Maximum 3% for branch circuits, 5% total (feeder + branch)
General recommendation: Keep voltage drop below 3% for optimal performance
Below 2%: Excellent — minimal power loss
2-3%: Acceptable for most applications
3-5%: May cause issues with sensitive equipment
Above 5%: Not recommended — equipment may malfunction

Frequently Asked Questions

To reduce voltage drop: (1) Use larger wire gauge (lower AWG number / higher mm²), (2) Shorten wire length, (3) Reduce load current, (4) Use copper instead of aluminum, (5) Increase source voltage if possible.

Copper has lower resistivity (0.0175 Ω·mm²/m) than aluminum (0.0283 Ω·mm²/m), meaning less voltage drop for the same wire size. However, aluminum is lighter and cheaper, making it suitable for long-distance power transmission.

Wire gauge depends on current rating, length, and acceptable voltage drop. For home wiring: 1.5 mm² for lighting (10A), 2.5 mm² for power sockets (16A), 4 mm² for high-power appliances (25A). Always consult local electrical codes.