Voltage Drop Calculator
Estimate feeder voltage drop using conductor size, current, run length and conductor material.
How this calculator works
This quick calculator estimates conductor resistance from material resistivity and cross-sectional area.
1 phase: Voltage drop = 2 × I × L × R.
3 phase: Voltage drop = sqrt(3) × I × L × R.
Cable reactance is not included. For large AC cables, long runs or critical design, use the manufacturer's R and X values and the applicable standard method.
Example
Long cable runs and smaller conductor sizes produce larger voltage drop for the same current.
Source and engineering note
BIS lists IS 732:2019 as the Code of Practice for Electrical Wiring Installations and IS 8130:2013 for conductors used in insulated electric cables and flexible cords. IEC 60364-5-52 covers selection and erection of wiring systems, including current-carrying capacity and voltage drop.
CalcSetu's cable tools are preliminary engineering estimates. Final cable selection must be verified against the actual cable manufacturer's current-carrying-capacity table, installation method, ambient temperature, grouping, harmonics, protective device and short-circuit withstand.
Bureau of Indian Standards - IEC 60364-5-52
Last reviewed: 27 August 2026.
Frequently asked questions
Does this include reactance?
No. It is a simplified resistive estimate. Detailed AC voltage drop can require both resistance and reactance.
Why does temperature matter?
Copper and aluminium resistance increases as conductor temperature rises.
Is one-way length used?
Yes. The formula handles the return path factor for single-phase and sqrt(3) relationship for three-phase.