Enter the dielectric constant, trace height, trace width, and trace thickness into the calculator to determine the PCB impedance.

PCB Impedance Formula

The following formula is used to calculate a PCB impedance for a microstrip.

Z = [ 87 / SQRT(e+1.41) ] * ln [ 5.98H / (.8W +T) ]

  • Where Z is the impedance
  • e is the dielectric constant
  • H is the trace height
  • W is the trace width
  • T is the trace thickness

PCB Impedance Definition

A PCB impedance is defined as the sum of reactance and resistance in a printed circuit board. PCB impedance is calculated use the dielectric constant, trace height, trade width, and trace thickness.

Example Problem

How to calculate PCB Impedance?

First, determine the dielectric constant. This should be provided along with the PCB material. For this example, we will use 2.2.

Next, determine the trace width. Measuring the trace width we get a width of 5mm.

Next, determine the trace height/length. This is found to be 10mm.

Next, determine the trace thickness. This is measured to be .5mm.

Finally, calculate the PCB impedance using the formula above.

Z = [ 87 / SQRT(e+1.41) ] * ln [ 5.98H / (.8W +T) ]

= [ 87 / SQRT(2.2+1.41) ] * ln [ 5.98(10) / (.8(5) +(.5)) ]

pcb impedance calculator