Voltage Drop Calculator
Calculate the voltage drop in electrical circuits based on wire material, size, length, and current. Essential for electrical engineering and wiring design.
Published by:
isCalculator Editorial Team
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How to use this tool?
This calculator estimates the voltage drop in an electrical circuit based on wire size, material, length, current, and phase. Use it to ensure your wiring meets safety and efficiency standards.
- Enter Source Voltage (V): Input the system voltage (e.g., 120V for a standard US outlet). Must be a positive number.
- Enter Load Current (A): Input the current drawn by the load in amperes (e.g., 10A). Must be positive.
- Enter One-Way Length (ft): Input the distance from the source to the load in feet. This is the one-way wire length, not the total round trip.
- Select Wire Material: Choose either Copper or Aluminum. Copper has lower resistance.
- Select Wire Size (AWG): Choose the American Wire Gauge (AWG) size from the dropdown (e.g., 12 AWG). Smaller AWG numbers mean thicker wire.
- Select Phase: Choose Single Phase (most residential) or Three Phase (commercial/industrial).
- Click "Calculate Voltage Drop": The results will show:
- Voltage Drop (V): The total voltage lost in the wire.
- Voltage Drop Percentage (%): The drop relative to the source voltage. For most circuits, keep this under 3% for branch circuits or 5% total.
Note: All inputs are in imperial units (volts, amperes, feet). The calculator uses standard resistance values per 1000 feet for each AWG size. Press Enter in any input field to calculate quickly.
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Frequently Asked Questions
Voltage drop is the reduction in voltage in an electrical circuit between the source and load due to wire resistance.
Typically, a voltage drop of 3% or less is acceptable for branch circuits, and 5% for total system.
Yes, longer wires result in higher voltage drop because resistance increases with length.