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Electricity Calculators

Voltage Drop Calculator

Voltage drop along a cable run from length, conductor size and current, with the percentage drop.

Enter values

Results update as you type.

Result

Voltage drop

6.451 V

Within the usual 3% guideline.

Percentage drop
2.8%
Voltage at the load
223.55 V
Cable resistance
0.4032 Ω
Power lost in the cable
103.22 W

Guidance only — follow your local wiring regulations and have electrical work done by a qualified electrician.

About the Voltage Drop Calculator

Voltage drop along a cable run from length, conductor size and current, with the percentage drop.

Also known as: cable voltage drop, wire voltage loss, volt drop calculator, cable size voltage drop.

How to use this calculator

  1. Enter conductor, conductor cross-section, one-way cable length, current and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

V_drop = 2 × ρ × L × I / A (single phase)

Worked example

Using the values pre-filled in the calculator above:

  • Conductor: Copper
  • Conductor cross-section = 2.5 mm²
  • One-way cable length = 30 m
  • Current = 16 A
  • Supply voltage = 230 V
  • System: Single phase (out and back)

the calculator returns:

  • Voltage drop: 6.451 V
  • Percentage drop: 2.8%
  • Voltage at the load: 223.55 V
  • Cable resistance: 0.4032 Ω