Voltage Drop Calculator

Voltage drop is the reduction in voltage in an electrical circuit between the source and load. It’s important because excessive voltage drop can cause equipment to malfunction, reduce efficiency, and create safety hazards. The National Electrical Code (NEC) recommends maximum voltage drop of 3% for branch circuits and 5% for feeders.

Voltage drop is calculated using the formula: VD = (2 × L × I × R) / 1000 for single-phase circuits and VD = (1.732 × L × I × R) / 1000 for three-phase circuits, where VD is voltage drop in volts, L is the one-way distance in feet, I is the current in amperes, and R is the resistance per 1000 feet of conductor.

The National Electrical Code (NEC) recommends maximum voltage drop of 3% for branch circuits and 5% for feeders. However, sensitive electronic equipment may require even lower voltage drop (1-2%) to operate properly. Always check the manufacturer’s specifications for critical equipment.

To reduce voltage drop, you can: 1) Use larger conductor size (lower AWG number), 2) Reduce the length of the circuit, 3) Decrease the current load, 4) Use a higher supply voltage, 5) Improve the power factor, or 6) Use conductors with lower resistance (copper instead of aluminum).

Three-phase systems typically have less voltage drop than single-phase systems for the same power transfer because the power is delivered over three conductors instead of two. The formula for three-phase voltage drop includes a factor of 1.732 (square root of 3) instead of 2 for single-phase systems.