EngineerHub.orgHow to use this calculator
Enter the circuit voltage, current, one-way length and conductor size. Select copper or aluminium and the circuit type.
Inputs
Results
Background
Engineering basis, equations, assumptions, interpretation and practical limitations for this calculator.
DC/single-phase uses the round-trip conductor length. Balanced three-phase uses the √3 relationship.
This simplified model treats conductor reactance as negligible and adjusts resistance with temperature.
- Voltage drop is not cable sizing by itself.
- Check current-carrying capacity, short-circuit protection, disconnection time, installation method and local rules.
- Large AC cables and long runs may require reactance.
Frequently Asked Questions
Practical questions about assumptions, inputs, interpretation and limitations.
Enter the one-way route length. The calculator applies the appropriate current path for DC, single-phase AC and balanced three-phase calculations.
There is no single universal value. Allowable or recommended voltage drop depends on the installation, circuit purpose and governing electrical rules or project standard.
Copper and aluminium resistance rises as conductor temperature increases. A warmer conductor therefore produces more voltage drop and I²R loss for the same current.
For a balanced three-phase circuit using line-to-line voltage and line current, the voltage-drop relationship uses the √3 geometry of the three-phase system. Single-phase and DC circuits use the outgoing and return current path.
No. Voltage drop is only one design check. Cable sizing and protective-device selection also require ampacity, installation method, ambient conditions, grouping, fault current, disconnection requirements and applicable electrical standards.