Voltage Drop Calculator
Calculate Voltage Drop
VD = 2 × I × R × L / 1000
Formula
VD = 2 × I × R × L / 1000 | % Drop = (VD / V_supply) × 100
Frequently Asked Questions
What is voltage drop?
Voltage drop is the reduction in voltage as current flows through wire resistance. Excessive voltage drop can cause equipment malfunction. The NEC recommends no more than 3% drop for branch circuits and 5% total.
How is voltage drop calculated?
VD = 2 × I × R × L / 1000, where I is current in amps, R is wire resistance in ohms per 1000 feet, and L is one-way distance in feet. The factor of 2 accounts for both the supply and return conductors.
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