Voltage Drop & Wire Size Calculator
Check voltage loss across copper or aluminum cables and find the recommended conductor size in $\text{mm}^2$ and AWG.
What does the Voltage Drop Calculator do and how to use it?
The Herramix Voltage Drop & Wire Size Calculator helps electrical engineers, solar installers, and technicians size cables accurately so voltage loss along a run stays within code limits.
Choose your circuit type (DC / single-phase AC or balanced 3-phase AC), conductor material (copper or aluminum), wire cross-section in $\text{mm}^2$ (with approximate AWG gauge), source voltage, load current in amps, and one-way cable length in meters. The tool immediately computes voltage drop in volts, percentage drop, load terminal voltage, and the minimum standard cable cross-section to stay under a 3% drop.
Usage example
Scenario: Supplying a single-phase 230 V, 16 A pump located 35 meters away using $4\text{ mm}^2$ (~12 AWG) copper wire.
Result: The voltage drop is 4.83 V (2.10%), delivering 225.17 V at the pump—well within the 3% limit.
Frequently Asked Questions
What is the maximum allowable voltage drop?
Electrical standards such as IEC 60364 and the NEC typically recommend keeping voltage drop below 3% for lighting and branch circuits and below 5% for power circuits.
Should I enter one-way cable distance or round-trip wire length?
Enter the one-way distance from the panel or power source to the load. The formula automatically multiplies by 2 for 2-wire single-phase/DC circuits and by $\sqrt{3}$ for balanced three-phase circuits.
Why is voltage drop especially critical in 12V or 24V solar systems?
In low-voltage DC systems (12 V or 24 V), losing just 1.5 V represents over 12% of a 12 V battery bank, which can trigger low-voltage cutoffs on inverters and charge controllers.