Microstrip Impedance Calculator

Provide values for three of the four parameters h, t, w, Z₀ and the relative permittivity of the dielectric. Click the button corresponding to the unknown parameter to calculate its value ( 0.1< w/h < 3.0; 1 < ε_r < 15).

Select the units for all dimensions: mm mils

 (Dielectric thickness)

mm mils

 (Trace thickness)

mm mils

 (Trace width)

mm mils

  (Relative permittivity)

 (Characteristic impedance)

 ohms

C₀    (Capacitance):

pF/cm pF/inch

T_pd  (Propagation delay time):

psec/cm psec/inch

Notes

• The formulas used here are taken from the Design Guide for Electronic Packaging Utilizing High-Speed Techniques (4th Working Draft, IPC-2251, February 2001)
  
• Range of valid parameters specified in the Design Guide: 0.1< w/h < 3.0; 1 < ε_r < 15
• Accuracy: For typical PCB parameters (ε_r = 4, h = 30 mil and t = 1.37 mil), the deviation of the calculated results from results obtained using a 2D numerical field solver, is listed below.
  

  Z₀

  0.1 < w/h < 0.2

  within 5%

  0.2 < w/h < 1.5

  within 2%

  1.5 < w/h < 2.0

  within 5%

  2.0 < w/h < 2.7

  within 10%

  2.7 < w/h < 3.0

  within 15%

  C₀

  0.1 < w/h < 0.2

  within 10%

  0.2 < w/h < 1.2

  within 5%

  1.2 < w/h < 2.0

  within 10%

  2.0 < w/h < 3.0

  within 5%