Easily calculate voltage drop for wires and circuits to ensure safe, efficient, and code-compliant electrical installations. Use our free Voltage Drop Calculator to get quick, precise results tailored to your project.
** Note to User**:
This voltage drop calculator is applicable only to NEC applications and is designed for applications using
AWG and KCMIL sizes only. It does not optimize conductor sizes for several different loads at various points
in a circuit. The total combined load and length of the circuit must be used. Consult with an engineer if your
application does not fit into one of the following categories and/or requires more complex engineering
calculations.
RESIDENTIAL MODE CALCULATIONS: All ampacity values are taken from NEC 310.15. The conductor characteristics
are taken from Chapter 9, Tables 8 & 9 of the NEC. The calculations used to determine the recommended
conductor sizes for branch circuits are based on 60°C ampacity ratings for circuits using conductors smaller
than 1/0 AWG. Circuits using conductors sized 1/0 AWG and larger are determined using 75°C ampacity ratings.
Calculations to determine service and feeder conductor sizes are based on overcurrent device ratings rather
than actual expected loads which are conservative and may yield oversized conductors. No calculations consider
temperature correction factors or conductor de-rating for number of current-carrying conductors in a raceway.
These calculations are not optimized for medium voltage or high voltage installations (2400 Volts or more).
These calculations do not apply to flexible cords.
When one of the Commercial User Modes is selected, the Southwire Voltage Drop Calculator allows all options to be modified and therefore allows results that may be inappropriate for use in residential installations. We do not recommend use of a commercial user mode if you are not an electrical professional.