Voltage Drop Calculator
Voltage drop and power loss along a cable.
V
A
m
mm²
How it works
Voltage drop = k × resistivity × length × current ÷ cross-section, with k = 2 for single-phase (out and back) and √3 for three-phase. Resistivity is 0.0175 Ω·mm²/m for copper and 0.0282 for aluminium at about 20 °C. Many codes recommend keeping total drop under 3–5%. For three-phase, enter the line-to-line voltage. Example: with the default values, voltage drop comes to 5.25 V.
FAQ
Is this calculator free?
Yes. No signup is needed and nothing you enter is stored.
Is the result exact?
Results are rounded for display. For financial, medical, or legal decisions, confirm with a professional.
Do my numbers leave my device?
No. The calculation runs in your browser.