Voltage Drop Calculator

System Type
Voltage (V)
Current (A)
Wire Length (ft)
Power Factor
Wire Material
Wire Size (AWG)
System Type
Voltage (V)
Current (A)
Wire Length (ft)
Power Factor
Wire Material
Max Voltage Drop %

Voltage Drop Calculator: Free Online Tool for Electrical Calculations

Calculate voltage drop in electrical circuits accurately with our professional-grade calculator. Perfect for electricians, engineers, and DIY enthusiasts working on residential, commercial, or industrial electrical projects.

📢 Quick Tip: The National Electrical Code (NEC) recommends keeping voltage drop under 3% for branch circuits and 5% for combined feeders and branch circuits for optimal efficiency.

Why Calculate Voltage Drop?

Voltage drop occurs when electrical current flows through wire conductors, causing resistance and decreased voltage at the load end. Proper calculation is crucial for:

  • Safety: Ensure electrical systems operate within safe parameters
  • Efficiency: Minimize power losses and reduce energy costs
  • Compliance: Meet NEC and local electrical code requirements
  • Performance: Maintain proper operation of electrical equipment

Calculator Features

NEC Data Calculator

Calculate voltage drop using precise NEC wire characteristics:

  • Support for multiple system types (1-phase, 3-phase)
  • Built-in wire resistance values
  • Common wire sizes from 14 AWG to 4/0
  • Copper and aluminum conductor options

Wire Size Calculator

Find the right wire size based on your requirements:

  • Automatic wire size recommendations
  • Custom voltage drop thresholds
  • Power factor consideration
  • Length and current optimization

How to Use This Calculator

  1. Select your system type (1-phase or 3-phase configuration)
  2. Enter the system voltage (in volts)
  3. Input the current draw (in amperes)
  4. Specify the conductor length (in feet)
  5. Adjust the power factor (default 0.85)
  6. Choose between copper or aluminum conductors
  7. Select wire size or desired maximum voltage drop

Important Considerations

While this calculator provides accurate results based on standard electrical principles, always:

  • Consult local electrical codes for specific requirements
  • Factor in ambient temperature and installation conditions
  • Consider future load growth in your calculations
  • Verify results with a licensed electrician for critical applications