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Voltage drop calculator
Enter the conductor size, circuit length, load current and system voltage to estimate the voltage drop and the percentage of the supply voltage. The tool uses IEC 60228 maximum DC resistance values; the final size is confirmed by your project engineer under the applicable wiring rules.
Estimate only: single circuit, 20 C conductor resistance, no reactance above 1 kV, no grouping or temperature corrections. Installation method and rating are confirmed by the project engineer.
IEC 60228 DC resistance table
| mm2 | Copper (Class 2) (ohm/km) | Aluminium (Class 2) (ohm/km) |
|---|---|---|
| 1.5 | 12.1 | – |
| 2.5 | 7.41 | – |
| 4 | 4.61 | – |
| 6 | 3.08 | – |
| 10 | 1.83 | 3.08 |
| 16 | 1.15 | 1.91 |
| 25 | 0.727 | 1.2 |
| 35 | 0.524 | 0.868 |
| 50 | 0.387 | 0.641 |
| 70 | 0.268 | 0.443 |
| 95 | 0.193 | 0.32 |
| 120 | 0.153 | 0.253 |
- Pick the conductor size and material - the tool reads the IEC 60228 maximum DC resistance at 20 C for Class 2 (stranded).
- Enter the load current and the one-way route length; three-phase uses the sqrt(3) factor, single phase uses 2.
- Read the drop in volts and as a percentage of the supply voltage; keep it inside the limit your wiring rules set for the circuit.