Calculate microstrip, symmetric stripline and conventional unbacked CPW impedance, with inverse design on each model’s own geometry variable.
Microstrip and stripline use IPC-2141A quasi-static formulas; CPW uses Wen’s conventional unbacked, semi-infinite-substrate simplification.
Enter the parameters and run the calculation to see results and model assumptions here.
Formulas, variables, and model boundaries are published. References last reviewed on 2026-08-30.
These equations directly produce the primary results and define the tool’s core model.
3Z₀ = (87 / √(εᵣ+1.41)) · ln(5.98 h / (0.8W + T))Quasi-static approximation applicable for 0.1 < W/h < 2.0.
Z₀ = (60 / √εᵣ) · ln(4 b / (0.67π (0.8W + T)))Characteristic impedance of a symmetric stripline equidistant from both reference planes.
Z₀ = (30π / √ε_eff) · K(k′)/K(k)，k = W/(W+2s)，ε_eff = (εᵣ+1)/2Wen’s conventional unbacked CPW quasi-static simplification; K(k) is the complete elliptic integral of the first kind evaluated with the Gauss arithmetic–geometric mean algorithm.
Results use the models and assumptions shown on this page for design estimates and pre-compliance risk review. Complex structures, dispersion, near-field coupling, and test setup can cause significant deviation.
Commonly via Hammerstad–Jensen approximations from W/h and dielectric εᵣ. Rule of thumb: a 50 Ω microstrip on 1.6 mm FR4 has W/h ≈ 1.8–2.
Z0 = (60 / √εᵣ) · ln(b / a), with b the inner diameter of the outer conductor and a the outer diameter of the inner conductor. 50 Ω corresponds to b/a ≈ 2.3.
To match instruments, connectors, and antennas into one impedance chain, avoiding reflections and standing waves. Impedance discontinuities also create slot antennas and raise EMI risk.
These tools support design-stage estimates. For accredited EMC testing, compliance decisions, and troubleshooting, contact us.