Why VoltageDrop
Voltage drop in volts and percent for copper or aluminum, single or three phase, AWG or mm² — plus reverse sizing to hit a target drop. NEC K-factor and IEC resistivity methods.
NEC & IEC
K-factor (12.9/21.2) and resistivity methods.
1φ & 3φ
Correct 2× and √3 factors.
AWG & mm²
Chapter 9 circular mils and IEC sections.
Reverse sizing
Pick the wire that meets your % target.
3% / 5% bands
Branch/feeder guidance badges.
Power factor
Impedance method with cosφ.
How it works
Enter the run
Voltage, current, one-way length.
Pick the wire
Or let the app size it for a target %.
Read the drop
Volts, percent and a clear verdict.
FAQ
Which method does it use?
NEC K-factor (2·K·I·L/CM) or IEC resistivity — your choice, with power-factor support.
One-way or round-trip length?
Enter one-way; the formulas handle the return path.
Is it verified?
Formulas and tables are covered by automated tests against published NEC/IEC values.
Who is it for?
Electricians, engineers and inspectors.