Microstrip differential Impedance Calculator

Tools - Pcbcupid - Simple and easy to use Microstrip differential impedance calculator

Microstrip are transmission lines that are routed on the external layers of the PCB which are always routed above a large reference plane on the adjacent layer. As the name suggests microstrip lines are used to convey microwave-frequency signals and RF signals. You can read more about microstrip here.

Differential impedance refers to the characteristic impedance between two lines when they are driven differentially (Like USB D+ and D-). To Calculate Input the values of characteristic impedance, trace height, and spacing between traces to obtain precise results. Understand the characteristics of your electrical transmission lines and optimize your circuit design.

Microstrip differential diagram pcbcupid

Understanding Microstrip differential impedance:

Microstrip differential impedance denotes the resistance to alternating current (AC) within a microstrip transmission line, a specific form of printed circuit board (PCB) trace. Constructed with a conducting strip, typically copper, atop a dielectric substrate such as FR4, the microstrip’s differential impedance arises from the cumulative impedance of both strips.

Factors Affecting Microstrip Differential Impedance:

Distance between strips: The separation between the two conducting strips has a direct impact on the differential impedance. When the distance is reduced, it results in higher capacitance and lower impedance.

Height of substrate: The height of the substrate plays a significant role in altering both the dielectric constant and impedance. Greater thickness in substrates results in higher impedance levels.

Trace thickness: The thickness of the conductive strip has an impact on both inductance and impedance, with thicker strips leading to higher impedance.

Dielectric constant of substrate:The capacitance and impedance are influenced by the substrate’s dielectric constant. Elevated dielectric constants lead to heightened impedance.

Frequency: The impedance is influenced by the frequency of the signal, with higher frequencies resulting in elevated impedance levels.

Importance of Microstrip Differential Impedance:

Signal integrity: Maintaining precise impedance control is essential in high-frequency circuits to preserve signal integrity, promote dependable data transmission, and minimize electromagnetic interference (EMI).

Noise reduction: Adequate management of impedance can mitigate signal interference and cross-channel talk, thereby enhancing the efficiency of the entire system.

Design optimization: Precise impedance computations empower designers to fine-tune PCB layouts tailored to particular needs, guaranteeing peak performance while reducing inaccuracies.


High-speed digital PCB design.

Differential signal transmission.

Ethernet, USB, and HDMI.

Power-handling capabilities.

Cross-talk reduction.

Unintentional radiation reduction.


In essence, comprehending the intricacies of microstrip differential impedance is pivotal in electronic design. Familiarity with its determinants, computation techniques, and significance is imperative for the creation of dependable and high-functioning PCBs.

Step – 1: Calculate the Characteristic Impedance (more Info)
Trace width
Trace thickness
Dielectric thickness
Relative dielectric constant
Step – 2: Calculate the differential Impedance
Characteristic Impedance
Space Between Traces
Height of Trace


\[ d = 2 * z \left( 1 – 0.48 * e^{-0.96 * \left( \frac {s}{h} \right)} \right) \]

where :

  • d = Differential Impedance
  • z = Characteristic Impedance / Single ended Impedance
  • s = Space between traces
  • h = Height of trace

Any questions? Drop them here!