Wire Size Calculator
Size by allowable voltage drop (DC/single-phase approximation)
How to Use This Calculator
Enter load current, one-way cable run length, supply voltage, allowable voltage drop percentage, and conductor material. The tool estimates the minimum cross-sectional area.
Formula
Vdrop = I · R = I · (ρ · 2L / A)
A ≥ ρ · 2L · I / Vdrop,allow
This is a DC/single-phase approximation. Three-phase uses similar logic with line-specific constants and return paths.
Frequently Asked Questions
Does this consider ampacity?
No. This tool sizes for voltage drop only. Always verify thermal ampacity per local codes.
Round trip or one-way length?
Enter the one-way length. The calculation uses 2L to account for the return path.