Via Size Calculator

Embed the Ohm’s law calculator on your website:

Illustration of hole diameter, plating thickness and via length are shown in the picture below . The algorithm they are using for calculating values of resistance, voltage drop, power loss, estimated ampacity and thermal resistance are shown below:


        Resistance = Resistivity*Length/Area
        Area = pi*(Inner_dia + Plating_thk)*Plating_thk
        Resistivity = 1.9E-6 Ohm-cm (plated copper)
        (plated copper is much more resistive than pure copper)
        Copper Thermal_Resistivity = 0.249 cm-K/W (at 300K)
        Est_Ampacity [Amps] = k*(Temp_Rise [deg C])^b*(Area [mils^2])^c
        For IPC-2221 external layers: k = 0.048, b = 0.44, c = 0.725.


  1. “Constructing Your Power Supply – Layout Considerations”, by Robert Kollman
  2. “Current Carrying Capacity of Vias”, by Doug Brooks and Dave Graves

Disclaimer: The calculations performed are for reference only.