120V Voltage DropCalculator
Calculate voltage drop for 120V AC residential and commercial circuits. NEC-compliant calculator for branch circuits and feeders.
AC Circuit Parameters
NEC Chapter 9 Table 9 values
Calculation Results
Warning - Consider larger wire size
120V Applications
- •Residential branch circuits
- •Lighting circuits
- •Small appliance circuits
- •Outdoor lighting
- •Garage and workshop wiring
- •HVAC equipment
AC Formula
Other Calculators
120V Voltage Drop Calculation Guide
About 120V Systems
120V AC systems are commonly used in residential and light commercial applications. Proper voltage drop calculations ensure equipment operates efficiently and safely within rated tolerances.
The NEC recommends limiting voltage drop to 3% for branch circuits and 5% total for the combination of feeder and branch circuit. For AC systems, this translates to a maximum drop of 3.6V for branch circuits.
Calculation Considerations
AC voltage drop calculations must account for both resistance and reactance of the conductors. The power factor of the load affects the effective impedance, making higher power factor loads more efficient from a voltage drop perspective.
For 120V systems, common wire sizes range from #14 AWG for lighting to #6 AWG for appliances. Always verify ampacity requirements alongside voltage drop calculations.