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