Voltage Drop Calculator
Use this direct voltage-drop workflow when you already know the conductor resistance basis. It estimates drop and margin against the entered limit but does not select a conductor or verify code compliance.
- Voltage drop
- V
- Voltage drop
- %
- Entered limit in volts
- V
- Voltage-drop margin
- percentage points
- Entered-limit status
Calculation details
- Phase multiplier
- x
- Calculation basis
- Selection boundary
Recent results
Formulas
- Phase multiplier = 2 for single-phase or DC two-wire; sqrt(3) for balanced three-phase
- Voltage drop volts = phase multiplier x current x one-way length x conductor resistance per 1000 ft / 1000
- Voltage drop percent = voltage drop volts / system voltage x 100
- Voltage-drop margin = entered drop limit percent - voltage drop percent
Use this calculator
Estimate voltage drop and voltage-drop percentage from load current, one-way length, system voltage, phase model, and conductor resistance.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This is a voltage-drop estimate using user-supplied resistance. It does not select conductor size, verify ampacity, apply NEC tables, evaluate termination temperature, or approve an installation.
FAQs
Is this different from the Wire Size Calculator?
Yes. This page owns direct voltage-drop intent when conductor resistance is known. The Wire Size Calculator focuses on a voltage-drop resistance target and selection boundary.
Does this pick an AWG or kcmil size?
No. Enter a verified resistance value for the conductor you want to evaluate. The result does not choose a conductor size.
Which phase model should I choose?
Use the two-conductor option for single-phase two-wire or DC loop estimates. Use balanced three-phase only when the entered voltage and load match that model.