Microstrip Trace Impedance Calculator

  1. Fill in the relative permittivity of the dielectric and the height, width, and thickness of the trace.
  2. Select the Calculate button to calculate the characteristic impedance of the trace and the effective relative permittivity.

If you leave the relative permittivity Er blank, a default microstrip dimension will be used, and the characteristic impedance and the effective permittivity are calculated after selecting the Calculate button. Selecting the Another Calculation button will clear the dimension fields and the result fields, then you can fill in the dimension of a new structure. If the dispersion is not considered (No is checked), the quasi-TEM approximation expressions are used to calculate Z0 and Eeff; while the well known Yamashita dispersion formula will be used to calculate Z0(f) and Eeff(f) if the dispersion is considered (Yes is checked). Equations used to make these calculations can be found in the book [1], and are also provided at the bottom of this page.

Units for dimension:
mm mils

er
mm
mm
mm
Calculation Results:
Z0 ohms
eeff

microstrip

The dispersion of the microstrip line can be accounted by the approximate dispersion formula, do you want to know the dispersion characteristic?
No Yes

If the dispersion is considered, please provide the frequency in MHz.
Frequency MHz


formula for microstrip structure formula for microstrip structure [1] K. Chang, "Handbook of Microwave and Optical Components", Vol 1,John Wiley & Sons, New York, p. 30, 1989.

The conductors on PCBs have rectangular cross sections, as opposed to wires, whose cross sections are circular. PCB are composed of a dielectric substrate (typical glass-epoxy with relative permittivity 4.7) on which rectangular cross-section conductors (lands) are etched. Typical board thickness are of order 50 mils. or 1.27 mm (1mil = 0.0254 mm, 1 mm=~40 mil). Land thicknesses are specified in terms of the thickness of the board cladding that was etched away to form the lands. Typical cladding thichnesses are 1 ounce (oz.) Cu and 2 ounce Cu. This refers to the weight of that thickness of the copper material that occupies an area of 1 spuare foot. For example, the thickness of 1 ounce Cu cladding is 1.38 mils (0.035052 mm), and a 1 square foot area would weigh 1 ounce. The thickness of 2 ounce Cu is double this, or 2.76 mils (0.070104 mm).

THE FORMULAS ARE APPROXIMATIONS!
They should not be used when a high degree of accuracy is required.
This calculator is developed by Kami Electromagnetic Compatibility Laboratory, UEC. Questions concerning this calculator or update information for this web site should be sent to email