The characteristic impedance (Zo) of a microstrip transmission line can be calculated using the active calculator or the formulas at the bottom of the page.
![[diagram of PCB layers]](../images/microstrip-drawing.gif)
The following formulas are from an article by Rick Hartley page 27 http://www.jlab.org/accel/eecad/pdf/050rfdesign.pdf
The formulas give results within 3% of the results obtained in http://www.polarinstruments.com/support/cits/IPC1999.pdf
More calculators for transmission line can be found at http://www.circuitsage.com/tline.html
![[calculation formula]](../images/microstrip-formula-hartley27.gif)
![[calculation formula]](../images/microstrip-formula2.gif)
Where εr is the Relative Dielectric Constant
W is the Width of track
t is the Thickness of track (1 oz/ft2 = 0.035 mm)
h is the Thickness of dielectric
This calculator is provided free by Chemandy Electronics in order to promote the FLEXI-BOX
Return to Calculator Index