⚡ Voltage Drop Calculator

Voltage drop is the reduction in voltage that occurs when electrical current flows through a conductor. It's caused by the resistance of the wire and can affect the performance of electrical equipment.

According to the National Electrical Code (NEC), the maximum voltage drop should not exceed 5% for branch circuits and feeders combined, with 3% recommended for branch circuits and 2% for feeders.

For DC circuits, use the formula: Voltage Drop = 2 × Current × Resistance × Distance. The factor of 2 accounts for both the hot and neutral conductors.

Copper has lower resistance and better conductivity than aluminum. Aluminum conductors need to be larger (lower AWG number) to carry the same current with the same voltage drop as copper.

Higher temperatures increase conductor resistance. Most calculations use resistance values at 75°C (167°F). Temperature correction factors should be applied for different operating temperatures.

Three-phase calculations use the factor √3 (1.732) instead of 2, because the voltage drop is measured line-to-line rather than line-to-neutral.

Select wire size based on both ampacity (current-carrying capacity) and voltage drop requirements. Choose the larger of the two requirements to ensure safe and efficient operation.

Ampacity is affected by conductor material, insulation temperature rating, installation method, ambient temperature, and the number of current-carrying conductors in a raceway.