Voltage Drop Calculator
Calculate voltage drop across electrical wires over distance. Enter wire size, length, load current, and conductor material for NEC compliant calculations. Essential for electrical safety and efficiency.
Why Voltage Drop Matters
Equipment Performance
Excessive voltage drop reduces motor efficiency, dims lights, and can damage sensitive electronics
NEC Compliance
National Electrical Code limits voltage drop to 3% for branch circuits and 5% total system
Cost Efficiency
Proper wire sizing prevents energy waste and reduces long-term operating costs
Voltage Drop Formula & Standards
Voltage Drop Formula
NEC Standards
Voltage Drop Calculator
Enter wire specifications to calculate voltage drop and NEC compliance
Residential Common Scenarios
Commercial Scenarios
Professional Electrical Work Opportunities
Using voltage drop calculations daily? Connect with electrical contractors nationwide who need skilled electricians for commercial, industrial, and residential projects.
Join 10,000+ electrical professionals earning more
Common Wire Sizes & Voltage Drop
Typical voltage drop per 100 feet for common wire sizes and loads. Use for quick estimates and planning.
Residential Applications
Commercial/Industrial
*Based on 120V single-phase copper conductors at 75°C. Color coding: Green = Good (<3%), Orange = Caution (3-5%), Red = Excessive (>5%)
Effects of Voltage Drop
Motor Performance
Reduced torque and efficiency
HighLighting
Dimmed lights, shorter bulb life
MediumHVAC Systems
Poor cooling/heating performance
HighElectronics
Malfunction, damage to sensitive equipment
CriticalEnergy Costs
Increased power consumption
MediumCode Compliance
NEC violations, failed inspections
CriticalJoin the Electrical Community
Connect with electrical professionals, share calculation tips, and advance your career. Join our active community for exclusive opportunities and industry insights.
Understanding Voltage Drop
What Causes Voltage Drop?
Voltage drop occurs when electrical current flows through a conductor's resistance, converting electrical energy to heat. The longer the wire or the higher the current, the greater the voltage drop. This is why wire sizing is critical for maintaining proper voltage at loads.
NEC Requirements
The National Electrical Code (NEC) limits voltage drop to 3% for branch circuits and feeders, with a total system limit of 5%. These limits ensure equipment operates efficiently and safely. Article 210.19(A)(1) and 215.2(A)(1) provide specific requirements for voltage drop calculations.
Copper vs Aluminum
Copper conductors have lower resistance (K=12.9) compared to aluminum (K=21.2), resulting in less voltage drop. While aluminum is less expensive, it requires larger wire sizes to achieve the same voltage drop as copper. Consider installation costs, termination requirements, and long-term performance when choosing conductor material.
Practical Applications
Electricians use voltage drop calculations for panel relocations, sub-panel installations, and long circuit runs. Engineers apply these calculations in building design and load analysis. Common applications include residential service upgrades, commercial lighting circuits, and industrial motor feeds.
Electrical Safety & Code Compliance
This calculator provides theoretical voltage drop calculations. Actual conditions may vary due to temperature, conduit fill, and ambient conditions. Always consult local electrical codes, follow NEC requirements, and verify calculations with licensed professionals. Proper installation and inspection are essential for electrical safety.
Ready to Advance Your Electrical Career?
Master voltage drop calculations and connect with electrical contractors seeking skilled professionals. Find better opportunities and grow your electrical career with the leading job board.
Trusted by 10,000+ electrical professionals nationwide