Voltage Drop Calculator
Calculate voltage drop in electrical circuits, analyze wire gauge requirements, and ensure NEC compliance for professional electrical installations.
Voltage Drop Calculator
Calculate voltage drop in electrical circuits, analyze wire gauge requirements, and ensure NEC compliance
Circuit Parameters
Environmental Factors
Voltage Drop Analysis
Final Voltage
At the load
Power Loss
Heat dissipation
NEC Compliance
3% branch circuit limit
Wire Resistance
Total circuit resistance
Recommendations
- • Voltage drop (10.6%) exceeds NEC 3% recommendation
- • Consider using 1 AWG wire to reduce voltage drop
- • Wire ampacity should be at least 125% of load current per NEC 210.20(A)
- • Voltage drop exceeds 5% - equipment may not operate properly
- • Always consult local electrical codes and a licensed electrician
- • Consider power factor correction if using reactive loads
Related Calculators
How to Use
- 1Enter your values in the input fields
- 2Review the calculated results
- 3Use the results for your planning
📚 Table of Contents
1Complete Guide to Voltage Drop
Calculate voltage drop in electrical circuits and wire sizing. This comprehensive guide will help you understand all aspects of voltage drop and how to use it effectively for your specific needs. Whether you're using this for personal, professional, or educational purposes, you'll find valuable insights and practical tips.
Getting Started
Understanding the basics ensures accurate results: • Input requirements and formats • Common use cases and scenarios • Interpreting output values • Troubleshooting common issues • Best practices for accuracy
Advanced Features
Maximize the calculator's potential: • Multiple calculation modes • Customization options • Saving and comparing results • Integration with other tools • Professional applications
2Tips and Best Practices
Get the most value from your calculations with these expert tips and strategies.
Accuracy and Precision
Ensure reliable results: 1. Double-check input values 2. Use appropriate units 3. Consider significant figures 4. Account for real-world variables 5. Verify with alternative methods when possible
Common Applications
This calculator helps with: • Planning and estimation • Comparison and analysis • Decision making • Problem solving • Educational purposes • Professional requirements
🔗 Related Resources
This comprehensive guide is regularly updated to ensure accuracy. Last reviewed: 7/25/2025
Frequently Asked Questions
What is voltage drop and why is it important?
Voltage drop is the reduction in voltage that occurs when current flows through wire resistance. Excessive voltage drop can cause equipment malfunction, reduced efficiency, and code violations. NEC recommends maximum 3% drop for branch circuits.
How do you calculate voltage drop?
For single-phase: VD = 2 × I × R × L. For three-phase: VD = √3 × I × R × L × cos(φ). Where I is current, R is resistance per foot, L is one-way length, and cos(φ) is power factor.
What wire gauge should I use to minimize voltage drop?
Wire gauge depends on current, distance, and acceptable voltage drop. Larger gauge (smaller AWG number) has lower resistance. Use the calculator to compare options and ensure NEC compliance.
What are NEC voltage drop requirements?
NEC recommends maximum 3% voltage drop for branch circuits and feeders separately, with 5% total combined. These are recommendations in NEC 210.19 and 215.2, not mandatory requirements.
How does temperature affect wire resistance?
Wire resistance increases with temperature at approximately 0.393% per °C above 20°C for copper. Higher temperatures reduce current-carrying capacity and increase voltage drop.
What is the difference between single-phase and three-phase voltage drop?
Single-phase uses VD = 2×I×R×L formula. Three-phase uses VD = √3×I×R×L×cos(φ) which is about 87% of single-phase drop for same current and distance.
When should I use larger wire gauge than ampacity requires?
Use larger gauge for long runs, sensitive equipment, efficiency improvement, future load growth, or when voltage drop calculations require it regardless of ampacity.