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Calcimator

Voltage Drop Calculator

Calculate voltage drop in electrical wiring based on wire gauge, length, current, and material. Ensure your circuits meet NEC recommendations.

Inputs

V
A
ft

Results

Voltage Drop

4.76 V

Voltage Drop %3.97%
Voltage at Load115.24 V
Wire Resistance0.32 Ω
Power Loss71.46 W
AssessmentMarginal (3-5%)
How to Use This Calculator
  1. Enter source voltage (V) and current (A).
  2. Set wire length (one-way, ft) and select AWG gauge from the dropdown.
  3. Review voltage drop (V), voltage drop (%), and voltage at the load (V).
  4. NEC limits voltage drop to 3% for branch circuits and 5% combined for feeders + branch circuits.
  5. If voltage drop exceeds limits, increase wire gauge (lower AWG number) or reduce run length.

How the result changes with Current

CurrentVoltage Drop
206.35 V
7022.23 V
13041.29 V
18057.17 V

What each input means

Source Voltage
Electrical potential difference in volts.
Current
Electrical current in amperes.
Wire Length (one-way)
Total length of the wire.
Wire Gauge (AWG)
Wire gauge (AWG).

How this is calculated

Formula

Voltage Drop = Current × Wire Resistance. Wire Resistance = (Resistivity × 2 × Length) / 1000. NEC recommends ≤3% drop for branch circuits.

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Source Voltage = 120, Current = 15, Wire Length (one-way) = 100, Wire Gauge (AWG) = 12 = 5 input(s) provided
  2. Calculate Voltage Drop
    Voltage Drop
    4.76 = 4.76
  3. Calculate Voltage Drop %
    Voltage Drop %
    3.97 = 3.97%
  4. Calculate Voltage at Load
    Voltage at Load
    115.24 = 115.24

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