Voltage Drop accuracy and testing

Formula source

• The formula used is **VD = 2 × L × R × I / 1000** for single-phase DC or AC (assuming power factor ~1). * **L:** Length (one way) in feet. * **R:** Resistance per 1,000 ft (from NEC Chapter 9, Table 8). * **I:** Current in Amperes.

Test cases

Known limitations

• This page documents the checked-in calculator logic and does not certify results for every real-world edge case.
• Use the result as a planning estimate unless the calculator page states a stricter purpose.

Assumptions

• The formula assumes a two-wire single-phase or DC circuit with a one-way entered length.
• Resistance values are approximate and based on standard per-1000-foot tables for the listed gauges.
• Voltage must be positive, and current and wire length cannot be negative.

Unit handling

• Voltage accepts values in V.
• Current (Amps) accepts values in A.
• Wire Length (one way) accepts values in ft.
• Wire Size (AWG) accepts one of the configured options.
• Wire Material accepts one of the configured options.
• Voltage Drop is displayed in V.
• Percentage Drop is displayed as a percentage.
• Voltage at Load is displayed in V.

Rounding rules

• Number displays use up to 2 decimal places in the calculator UI.
• Percent outputs are displayed with two decimal places.

Version history

Change log