Voltage Drop Calculator
Enter your wire gauge, current, length, and system voltage to see how much voltage you'll lose along the run.
Enter your wire gauge, current, length, and voltage to see results.
Based on standard AWG copper wire values (NEC Chapter 9, Table 8). For DC circuits only. Estimates for general planning purposes — always verify against your specific application's standards and your wire/connector manufacturer's specifications.
How This Is Calculated
Voltage drop happens because every wire has some electrical resistance, and that resistance increases with wire length and decreases with wire thickness (gauge). This tool uses the standard formula:
Voltage Drop = (2 × K × I × L) / CM
where K is the resistivity constant for copper (12.9), I is current in amps, L is one-way length in feet, and CM is the wire's cross-sectional area in circular mils, based on standard AWG values from NEC Chapter 9, Table 8.
This calculator covers DC, copper-conductor circuits. For a deeper look at how current and voltage ratings work, see Connector Current and Voltage Ratings Explained.