About Voltage Drop Calculator & NEC Compliance
Size long cable runs to prevent excessive voltage drop and equipment malfunction. Computes single-phase and three-phase voltage drops for copper and aluminum conductors according to NEC Chapter 9 Table 8 guidelines.
Key Capabilities & Features
- Supports 1-Phase (2L) and 3-Phase (√3) circuit topologies
- Accurate resistivity factors for Copper (K = 12.9) and Aluminum (K = 21.2)
- Evaluates National Electrical Code (NEC) 3% branch and 5% total drop limits
- Calculates terminal delivered voltage, percentage loss, and wasted conductor wattage
- Automatic recommendation for upsized wire gauge to achieve ≤3% drop
How to Use Voltage Drop Calculator & NEC Compliance
Enter Circuit Parameters
Specify nominal voltage, load amperage, and one-way run length in feet.
Select Conductor & Gauge
Pick copper or aluminum wire material and desired AWG gauge.
Check Compliance
Verify whether the voltage drop meets the NEC recommended 3% limit and view upsized gauge if needed.
Privacy & In-Browser Execution Guarantee
100% client-side execution with zero external data transmission.
Frequently Asked Questions
What is the maximum allowable voltage drop under the NEC?
NEC Informational Note 210.19(A) recommends that voltage drop on branch circuits should not exceed 3%, and total drop across feeders and branch circuits combined should not exceed 5% for optimal efficiency.
Why does voltage drop increase with longer distance?
Every wire conductor possesses electrical resistance proportional to its length. As distance increases, cumulative conductor resistance creates an IR potential drop that lowers terminal voltage.