Wire Size Calculator
Size by allowable voltage drop (DC/single-phase approximation)
Instructions
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.
Common 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.