Voltage drop calculator

Voltage lost along a cable run — from wire gauge, length, and current, for DC and AC circuits.

Voltage drop across a cable run — size the run before the load browns out.

Resistivity: Cu 1.72e-8 Ω·m, Al 2.82e-8 at 20 °C. Runs in this browser.

How to use

  1. Pick conductor (copper/aluminum) and enter the wire cross-section in mm².
  2. Enter one-way length, current, and system voltage.
  3. Read drop, % drop, and pass/3 % check.

What it supports

Wire size is entered directly as a cross-section in mm² up to 2,500 mm² (no AWG table); voltage ≤10,000 V, current ≤5,000 A, one-way length ≤10,000 m. Resistivity at 20 °C (Cu 1.72e-8, Al 2.82e-8 Ω·m), round-trip for DC/single-phase, √3 for three-phase. Conductor heating at high currents is not modeled.

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