Voltage Drop Calculator

Calculate voltage drop, wire size, maximum current, and wire length for electrical circuits.

Your Input

Select a calculation type, enter your circuit parameters, then click Calculate to see voltage drop, wire size, max current, or max length with step-by-step solution.

Complete User Guide

What is Voltage Drop?

Voltage drop is the reduction in voltage in an electrical circuit due to the resistance of the conductors. It's important to keep voltage drop within acceptable limits to ensure proper equipment operation.

How to Use

  1. Select calculation type
  2. Enter circuit parameters
  3. Select wire size and material
  4. Click Calculate to see results and step-by-step solution
  5. Use Reset to clear and hide results

Circuit Types

DC: Direct current circuits

Single-Phase AC: Standard residential AC power

Three-Phase AC: Commercial and industrial power

Wire Materials

Copper: Lower resistance, higher cost

Aluminum: Higher resistance, lower cost

Formulas

DC Voltage Drop:

VD = I × R × 2

Single-Phase AC:

VD = I × R × 2 × PF

Three-Phase AC:

VD = I × R × √3 × PF

Resistance:

R = (ρ × L) / A

Acceptable Voltage Drop

NEC recommends:

• 3% for branch circuits

• 5% for combined feeder and branch circuits

• Lower is better for sensitive equipment

Power Factor

Power factor is the ratio of real power to apparent power. For resistive loads (heaters, incandescent lights), power factor is 1.0. For inductive loads (motors, transformers), power factor is typically 0.7-0.9.

Important Notes

  • Voltage drop increases with wire length
  • Larger wire sizes reduce voltage drop
  • Copper has lower resistance than aluminum
  • Three-phase has lower voltage drop than single-phase
  • Always follow local electrical codes
  • Consider temperature derating

Common Applications

  • Electrical circuit design
  • Wire sizing for installations
  • Troubleshooting voltage issues
  • Long distance wiring
  • Solar panel installations

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