Advanced Voltage Drop Calculator

Calculating voltage loss accurately requires more than just knowing the wire size and distance. In real-world applications, factors like AC magnetic reactance, power factor, and parallel conductor setups drastically change your end-of-circuit voltage. Our Advanced Voltage Drop Calculator processes all of these variables to give you professional-grade results for both Imperial (AWG) and Metric (mm²) systems.

How to Use the Calculator

1. Set your electrical phase: Choose between DC, Single-Phase AC, or 3-Phase AC. Note: Selecting an AC phase will automatically unlock advanced fields for Conduit Material and Power Factor.
2. Adjust AC settings (if applicable): Select your conduit type (steel increases AC impedance) and enter your circuit's Power Factor (0.85 is a standard default for motor loads).
3. Select wire material and size: Choose copper or aluminum, then pick your wire size. The tool will automatically calculate and fill the standard wire impedance for that size. You can also manually override this resistance and change the unit (e.g., Ω/km or Ω/1000ft).
4. Enter parallel conductors: If you are running multiple wires per phase to reduce drop, enter that number (default is 1).
5. Input circuit details: Enter your source voltage, total load current (Amps), and the one-way distance of the cable run.
6. Calculate: Click the button to instantly see the total voltage lost, percentage drop, and end voltage.

The Advanced Formulas

To provide accurate results across mixed units and complex AC environments, our calculator determines the total impedance of the run before factoring in the load and phase multipliers. The core equations used are:

• Total Impedance (Z): Z = (Wire Resistance per unit × Distance) × Conduit Factor × Power Factor
• Voltage Drop (VD): VD = (Phase Multiplier × Current × Total Impedance) / Parallel Conductors
• Percentage Drop: %VD = (VD / Source Voltage) × 100

Constants & Multipliers Used:

• Phase Multiplier: 2 for DC and Single-Phase AC; 1.732 (√3) for 3-Phase AC.
• Conduit Factor (AC Only): 1.15 for Steel (Magnetic) conduit; 1.0 for PVC (Non-Magnetic).
• Imperial K-Values (at 75°C): 12.9 for Copper; 21.2 for Aluminum.
• Metric Conductivity (m/Ω·mm²): 56 for Copper; 35 for Aluminum.

Acceptable Limits & Solutions

The National Electrical Code (NEC) recommends a maximum voltage drop of 3% for branch circuits and 5% for total combined feeder and branch circuits. If your drop is too high, try:

• Increasing the wire size (smaller AWG number or larger mm²).
• Adding conductors in parallel to distribute the impedance.
• Switching from a magnetic (steel) conduit to non-magnetic (PVC) to reduce AC reactance.