Voltage Drop Calculator (AC & DC)

Prevent equipment failure by calculating power loss over long distances.

Parameters

Voltage

System Voltage

The nominal circuit voltage (e.g., 120V, 480V).

Phase

Circuit Phase

Single Phase (AC) or Three Phase. Affects the voltage drop formula constant.

Conductor Material

Wire Material

Copper is standard. Aluminum is lighter/cheaper but requires larger sizes.

Conduit Type

Conduit Material

Steel/Magnetic conduit increases voltage drop for large wires (1/0+).

Wire Size

Conductor Size

AWG or kcmil size of the conductor.

Parallel Sets (Runs)

Parallel Runs

Number of conductors per phase run in parallel to share the load.

One-Way Distance

Run Length

The one-way length of the circuit from source to load.

(FT)

Load Current (Amps)

Load Current

The actual current (Amps) flowing through the circuit.

Waiting for Input

Select Voltage

Voltage at Load

The remaining voltage available at the equipment terminals.

Standard Recommendation

Drop should not exceed 3% individually, or 5% combined.(Standard Practice)

Popular voltage drop Configurations

500ft Driveway Gate Voltage Drop Parking Lot Lights 277V Voltage Drop 300ft Well Pump Wire Size 150ft Shed Feeder Voltage Drop

Voltage Drop Formula

V_drop = (2 × L × R × I) / 1000

NEC Voltage Drop Limits (2020/2023)

According to NEC 210.19(A) Informational Note No. 4, branch circuits should not exceed 3% voltage drop. Combined feeder and branch circuits should not exceed 5% total voltage drop to ensure efficient operation.

Frequently Asked Questions

Does wire size affect voltage drop?

Yes. Larger wires have less resistance (lower Ohms/kFT), which reduces voltage drop. Increasing wire size is the most common way to fix voltage drop issues. Use our Wire Size Calculator to find the right wire for your ampacity.

Why does distance matter in wiring?

Voltage drop is directly proportional to distance. The further the current travels, the more resistance it encounters, causing voltage to "drop" before reaching the load.

What is the difference between Copper and Aluminum voltage drop?

Aluminum has higher resistance than Copper for the same size. Therefore, Aluminum wires will experience more voltage drop and typically need to be upsized to match the performance of Copper.

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