⚡ EE Calcs

Microstrip Impedance Calculator

Estimate characteristic impedance from stackup geometry.

GND plane εr dielectric w h t Z0 Z0 = 87/√(εr+1.41) · ln(5.98h/(0.8w+t))

Values

Result

Z0 ≈ 108 Ω (approximation)

Microstrip impedance

Microstrip is a trace over a ground plane, separated by the PCB dielectric. Its characteristic impedance depends on the dielectric constant, substrate height, trace width, and copper thickness. This calculator uses the standard closed-form approximation:
Z0 = 87/√(εr+1.41) · ln(5.98·h / (0.8·w + t))

It's accurate for typical hobbyist FR-4 geometries (0.1 < w/h < 3.0). For controlled-impedance production work, have the fab verify with their stackup and its exact εr.