FORMULA
Calculation method
Three phase: ΔV = √3 × I × L × (R cosφ + X sinφ) · Single phase: ΔV = 2 × I × L × (R cosφ + X sinφ)
For long circuits, ampacity alone may be insufficient; voltage drop can require a larger conductor.
CABLE CALCULATION
Voltage Drop Calculator
Calculate voltage drop in volts and percent for single or three-phase circuits using length, current, conductor size, resistance and power factor.
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CALCULATOR
Voltage drop calculation
R ≈ 7,410 Ω/km
Voltage drop5,18 V
Drop ratio1,29 %
iResistance is an approximate value near a 20 °C conductor temperature. Cable type, operating temperature, harmonics and installation method affect the result.
FREQUENTLY ASKED
About this calculation
How should line length be entered?
Enter the one-way length from source to load. The return path is included in the single-phase formula.
What voltage-drop limit should be used?
The limit depends on the application and applicable standard. 3% and 5% are common preliminary checks.
ENGINEERING NOTE
Fast calculation, clear assumptions, correct interpretation
The tools are intended for preliminary assessment and checking. Alongside each result, we explain the formula, assumptions and field conditions that require attention.
Prepared by: Neo Kontrol Otomasyon · Last technical review: July 2026
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