How to enter a wire run
Enter the electrical values first, then choose the wire details that match the run. The calculator uses Current, One-way length, Length unit, Conductor material, Wire gauge (AWG), Conductor temperature (°C), Circuit type, and Supply voltage (V) to calculate the drop and the voltage at the load.
- Enter Current, One-way length, and Supply voltage (V).
- Choose Length unit: Feet, Meters, or Centimeters.
- Choose Conductor material and Wire gauge (AWG), then set Conductor temperature (°C).
- Choose Circuit type: DC / single-phase or Three-phase.
- Click Calculate, then review Formula & steps and Assumptions. Use Copy result or Download result (.txt) to save the output.
What the result includes
After Calculate, the result lists Voltage drop, Voltage drop %, Received voltage, and Circuit resistance. Circuit resistance comes from the selected material, Wire gauge (AWG), Conductor temperature (°C), length, and Circuit type.
Inputs: 20 A, 50 Feet, Copper, 12 AWG, 75 °C, DC / single-phase, 120 V
Voltage drop: 3.853839 V
Voltage drop %: 3.211533%
Received voltage: 116.146161 V
Circuit resistance: 0.192692 ΩFormula & steps and Assumptions appear below those values. The calculator adds a warning when Voltage drop % exceeds 5%. It also warns that the estimate does not check conductor ampacity.
How circuit type changes the calculation
Enter the distance from the source to the load once in One-way length. For DC / single-phase, the calculator doubles that length for circuit resistance. For Three-phase, it multiplies the length by √3. Feet, Meters, and Centimeters are converted to meters before the calculation.
V_drop = I x R
R = rho(T) / A x L_circuitThe Wire gauge (AWG) list contains sizes from 18 AWG through 4/0 AWG. The calculation derives conductor area from the AWG geometric formula and adjusts bulk resistivity for the selected Conductor temperature (°C).
Input limits and assumptions
Current, One-way length, and Supply voltage (V) must be positive, valid numbers. Conductor temperature (°C) must stay between -40°C and 250°C. Values above 1,000,000,000,000 are rejected. An invalid or incomplete entry hides the result and shows an error.
The calculation assumes the selected Conductor temperature (°C), unity power factor, and bulk conductor resistivity. Reactance and skin effect are not modeled. The calculator does not apply a specific electrical code or check ampacity. Reset hides the result and restores Meters, Copper, 12 AWG, 75°C, and DC / single-phase; numeric fields stay as entered.
How to save the calculated result
After a valid calculation, the page fills the Copyable text result field with the displayed values, Formula & steps, Assumptions, and any warnings. Copy result sends that text to the clipboard when copying succeeds. Download result (.txt) creates a text file named voltage-drop-calculator-result.txt.
Related electrical calculators
This page belongs to Science Calculators. Use the Electrical Calculator for watts, volts, amps, resistance, resistor combinations, wire-size estimates, battery runtime, battery-bank sizing, or energy consumption. Use the Ohm's Law Calculator when you need voltage, current, resistance, or power from any two values. Use the Battery Runtime Calculator when runtime is the unknown and the inputs are capacity, load, voltage, and efficiency.
Frequently asked questions
How do I calculate voltage drop with this calculator?
Enter Current, One-way length, Conductor material, Wire gauge (AWG), Conductor temperature (°C), Circuit type, and Supply voltage (V), then click Calculate. The result shows the drop, percentage, received voltage, resistance, steps, and assumptions.
Should I enter one-way or round-trip wire length?
Enter One-way length, measured from the source to the load. DC / single-phase applies a factor of 2, while Three-phase applies √3 automatically.
What does Voltage drop % mean?
Voltage drop % is the calculated voltage loss divided by Supply voltage (V), multiplied by 100. The calculator adds a warning above 5%; the warning does not apply an electrical code.
Can I use this voltage drop calculator for three-phase wire?
Choose Three-phase under Circuit type and enter One-way length once. The calculation uses √3 times that length for effective circuit resistance.