01 / Microstrip calculator
Start with your stackup.
Estimate impedance, or solve the trace width for a target.
Use a design Dk appropriate to your laminate, construction and frequency. The 3.66 default is an example, not a universal laminate value.
Characteristic impedance
Hammerstad–Jensen quasi-static microstrip model; zero copper thickness, no solder mask, no dispersion or loss correction. Isolated microstrip only—not grounded coplanar waveguide. Validate the final geometry with your fabricator and an appropriate field solver. Model reference ↗
How to use this RF PCB design calculator
- Enter the dielectric constant recommended for design at your frequency and construction.
- Set the dielectric height between the signal trace and its reference plane. This is not necessarily the total board thickness.
- Enter a candidate trace width to estimate impedance, or enter a target impedance and solve the width.
- Use guided wavelength as a phase-length reference. It is not a ready-to-build antenna dimension.
- Save the inputs and review the finished geometry with the fabricator.
What the model includes
The calculator implements the quasi-static Hammerstad–Jensen microstrip formulation with an effective dielectric constant. It represents an isolated conductor above a ground plane with an air region above the trace. Its geometry is intentionally simple, making it useful for estimating trends and comparing early stackup options.
What it does not predict
The model does not account for copper thickness, roughness, solder mask, dielectric dispersion, nearby ground, losses, vias, bends or connectors. A coplanar trace with side grounds needs a different model. At high frequency, dimensions and discontinuities that look small on a board can be electrically significant.
Interpreting a result
A narrower trace normally raises microstrip impedance when the remaining stackup is fixed. Increasing the dielectric height also changes the ratio between width and height. Changing frequency here changes wavelength; the calculated impedance remains quasi-static. That is a model assumption, not proof that a physical trace has no dispersion.
A calculated 50 Ω is a design estimate. A finished-board impedance requirement needs agreed tolerances, measurement method and an appropriate coupon.
Microstrip model documentation
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