3-Phase Cable Voltage Drop Calculator
Check whether the cable run is too long for the load.
Your numbers
Your results
3-Phase Cable Voltage Drop Calculator by TheCalcTools
How the 3-Phase Cable Voltage Drop Calculator works
Choose the conductor material, size, length and load current.
Resistance per metre is resistivity ÷ area; reactance is taken as about 0.08 mΩ/m.
Voltage drop = √3 × I × L × (R cosφ + X sinφ) for three-phase, 2 × I × L × (…) for single-phase.
The formula
Worked example
Using the default values shown in the calculator:
| Conductor | Copper (~0.0225 Ω·mm²/m at 70°C) |
|---|---|
| Conductor size (mm²) | 35 |
| One-way length (m) | 80 |
| Load current (A) | 60 |
| Power factor | 0.85 |
| Supply | Three-phase 400 V |
- R = 0.0225 ÷ 35 = 0.000643 Ω/m.
- ΔV = √3 × 60 × 80 × (R cos φ + X sin φ) = 4.89 V (1.22%). Cable loss ≈ 555 W.
Result:
| Voltage drop (V) | 4.89 |
|---|---|
| Voltage drop (%) | 1.22% |
| Cable loss (W) | 555 |
| Check | Within 5% (typical limit) |
Frequently asked questions
What is an acceptable voltage drop?
Many standards limit total drop from source to load to around 5%, sometimes 3% for lighting. Check your local code.
Is this accurate?
It is an estimate. Use cable manufacturers’ tables for exact resistance and reactance, installation method, temperature and grouping factors.
Sources and further reading
Related calculators
More in Telecom Power & Passive Infrastructure · All calculators
This calculator gives estimates for planning only. Electrical installations must be designed, checked and carried out by qualified personnel following local codes and the equipment manufacturer's data. Never rely on this result alone for safety-critical decisions. See our disclaimer.