🖥️ PCB Impedance Calculator
Estimate the characteristic impedance of a surface microstrip PCB trace using its width, thickness, and the board’s dielectric properties.
What this calculator does
PCB traces carrying high-speed or RF signals need a controlled characteristic impedance (commonly 50Ω single-ended) so signals reflect and distort as little as possible. This calculator estimates the impedance of a surface microstrip trace — a trace on the outer layer running over a reference ground plane.
The formula
It uses the widely referenced IPC-2141-style microstrip approximation: Z0 = (87 / √(Er + 1.41)) × ln(5.98H / (0.8W + T)), where H is the dielectric height to the reference plane, W is trace width, T is copper thickness, and Er is the board’s dielectric constant (about 4.5 for standard FR-4).
This is a fast estimate for early design and hand-checking; it is not a substitute for a field-solver tool when building tightly controlled-impedance boards for production, especially at very high frequencies or unusual stack-ups.