Southwire Voltage Drop Calculator
Calculate voltage drop in electrical circuits based on wire size, length, current, and system type. Ensures compliance with NEC recommendations.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Southwire Voltage Drop Calculator
- Select Conductor Material: Choose Copper or Aluminum from the dropdown. This affects the resistivity constant used in calculations.
- Choose System Type: Pick Single-Phase or Three-Phase to match your electrical system.
- Pick Wire Size (AWG): Select the American Wire Gauge (AWG) from 14 AWG to 4/0 AWG. Larger AWG numbers mean thinner wires.
- Enter One-Way Length: Input the distance from the power source to the load in feet. Use whole numbers or decimals.
- Enter Load Current: Provide the circuit amperage in amperes (A). Use decimals if needed (e.g., 20.5).
- Enter Source Voltage: Input the nominal system voltage in volts (V) (e.g., 120, 240, 480).
- Calculate: Click the Calculate Voltage Drop button to see results.
Understanding Results:
- Voltage Drop (V): The actual voltage lost along the wire.
- Voltage Drop (%): Percentage relative to source voltage.
- Status: Indicates if drop is acceptable (≤3%), marginal (3-5%), or exceeds 5% (requires design change).
- Formula: Shows the exact calculation used for verification.
Note: All inputs must be positive numbers. Length is in feet (imperial). The calculator uses NEC recommended limits.
Previous Results
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Frequently Asked Questions
Voltage drop is the decrease in electrical potential along a conductor due to its resistance. Excessive drop can cause equipment malfunction.
NEC recommends no more than 3% drop for branch circuits and 5% total including feeders.
Yes, it uses standard resistivity values for copper and aluminum, similar to Southwire's methodology.