Voltage Drop Calculator
Professional voltage drop calculator for electricians, engineers, and technicians. Calculate cable voltage drop, end voltage, and percentage loss for copper and aluminum conductors in single-phase and three-phase systems.
Free Voltage Drop Calculator
What Is Voltage Drop?
Voltage drop is the reduction in electrical voltage that occurs when current flows through a conductor. Every electrical cable has resistance, which creates energy losses and reduces voltage at the load.
Excessive voltage drop can reduce equipment efficiency, cause overheating, increase power losses, and shorten the lifespan of electrical devices.
Voltage Drop Formula
The voltage drop formula depends on whether the electrical system is single-phase or three-phase.
Single-Phase Voltage Drop Formula
Three-Phase Voltage Drop Formula
Formula Variables
- VD = Voltage Drop (V)
- ρ = Resistivity of conductor material
- I = Current (A)
- L = Cable Length (m)
- S = Cable Cross-Sectional Area (mm²)
Recommended Voltage Drop Limits
- Maximum recommended branch circuit voltage drop: 3%
- Total feeder and branch circuit voltage drop should not exceed 5%
Maintaining proper voltage levels improves electrical system performance and reduces energy losses.
Applications of Voltage Drop Calculations
- Residential electrical installations
- Commercial power systems
- Industrial motor circuits
- Solar energy systems
- Generator installations
- Long-distance cable runs
- Electrical feeder sizing
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International Electrical Standards & References
NFPA
Publisher of the National Electrical Code (NEC), one of the most important electrical safety standards.
IEEE Standards
International engineering standards for electrical, industrial, and power system applications.
IEC Standards
Global electrical and electrotechnical standards used in industrial and commercial installations.
Combining accurate voltage drop calculations with international electrical standards helps improve safety, reduce power losses, and ensure reliable operation of electrical systems.