Please enter all required values.
RESULTS
Input Parameters Specification
Trace ThicknessCopper trace thickness used in impedance correction. Thicker copper changes effective conductor width and stripline impedance.
Substrate HeightDistance between reference planes in symmetric stripline geometry. This is a major PCB stack-up dimension.
Trace WidthConductor width embedded between ground planes. Wider traces generally reduce characteristic impedance.
Dielectric ConstantRelative permittivity of PCB material. FR4, Rogers, PTFE and ceramic laminates can produce different impedance values.
Practical Operational Examples
RF PCB Routing
Use this calculator to estimate stripline characteristic impedance inside multilayer boards for RF feeds, clocks and controlled impedance nets.
Impedance Matching
Adjust width, thickness or dielectric height to target 50 Ω, 75 Ω or another controlled impedance value.
Multilayer Stack-Up Check
Compare different substrate heights and dielectric constants before final PCB fabrication.
High-Speed Signal Design
Estimate embedded transmission line impedance for digital buses, RF modules, filters and microwave PCB sections.
Diagrams & Theory
A symmetric stripline has one conductor centered between two reference planes. The electric field is contained mostly inside the dielectric, making it useful for controlled RF and high-speed PCB routing. Because both reference planes surround the trace, stripline routing can provide better shielding than a surface microstrip trace.
Formulas & Mathematical Logic
Step 1: Convert trace thickness, substrate height and trace width using the selected unit multipliers.
Step 2: The calculator preserves the supplied symmetric stripline impedance logic and unit multipliers.
Step 3: Effective width correction is applied using trace thickness, substrate height and trace width.
Step 4: Impedance is calculated using dielectric constant and symmetric stripline geometry.
Step 5: The result is displayed as characteristic impedance in ohms.
Practical meaning: wider trace and higher dielectric constant usually reduce stripline impedance, while larger spacing between reference planes can increase impedance.
Step-by-Step Example
Example: trace thickness = 1 mil, substrate height = 20 mil, trace width = 8 mil, dielectric constant = 4.2.
The calculator first converts each input using the selected unit multipliers.
Trace thickness is used for effective width correction.
The corrected geometry is applied to the symmetric stripline impedance equation.
The dielectric constant is used to scale impedance for the PCB material.
The final impedance result is shown in ohms.
How to Use This Calculator
Enter copper trace thickness and select the correct unit.
Enter substrate height between the reference planes.
Enter the embedded trace width.
Enter dielectric constant of the PCB material.
Click Calculate to get symmetric stripline impedance.
Compare the result with your controlled impedance target before final routing.
About This Calculator
Estimate controlled impedance for centered stripline PCB routing.
The CalcBoy Symmetric Stripline Impedance Calculator calculates characteristic impedance from trace thickness, substrate height, trace width and dielectric constant.
Symmetric stripline is a transmission line structure where a copper trace is embedded between two reference planes, usually ground planes, with roughly equal dielectric spacing above and below the conductor. This geometry is widely used in RF PCB design, microwave routing, high-speed digital boards and controlled-impedance multilayer layouts.
Unlike a surface microstrip, most of the electric field in a stripline is contained inside the dielectric material. This can improve shielding and reduce radiation, but the impedance depends strongly on the PCB stack-up. Trace width, copper thickness, dielectric constant and reference-plane spacing must be selected carefully when targeting common values such as 50 ohms or 75 ohms.
This calculator is useful for RF engineers, PCB designers, embedded hardware designers and repair engineers who want a quick estimate before checking the final stack-up with a PCB manufacturer. For production work, always confirm impedance with the board house because real copper plating, dielectric tolerance, glass weave and lamination process can shift the final value.
Best UseSymmetric stripline impedance checks for multilayer PCB routing.
Supported InputsTrace thickness, substrate height, trace width and dielectric constant.
Helpful ForRF feeds, high-speed signals, clock lines, microwave traces and controlled impedance nets.
Design ReminderUse PCB manufacturer stack-up data for final impedance confirmation.
Tip: For accurate controlled impedance, ask the PCB manufacturer for the real dielectric thickness and dielectric constant of the exact laminate stack-up.
Frequently Asked Questions
What is symmetric stripline impedance?
It is the characteristic impedance of a centered conductor embedded between two reference planes in a multilayer PCB.
Why is stripline used in RF PCB design?
Stripline keeps most of the field inside the dielectric, which can reduce radiation and provide better shielding than surface routing.
What affects stripline impedance?
Trace width, copper thickness, dielectric constant and distance between reference planes all affect impedance.
Does wider trace reduce impedance?
Yes. Increasing trace width generally lowers characteristic impedance.
Can I use this for 50 ohm PCB routing?
Yes, it can estimate geometry for 50 ohm stripline routing, but final values should be confirmed with PCB manufacturer stack-up data.
Is this the same as microstrip impedance?
No. Microstrip is on an outer layer over a reference plane, while stripline is embedded between two reference planes.
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