Stripline Calculator
Symmetric and offset stripline — trace fully embedded between two ground planes. Computes Z₀, wavelength, λ/4 length, phase velocity, and dielectric + conductor attenuation. Uses the Wadell closed-form model. εeff = εr exactly (homogeneous dielectric).
We = W + (t/π)·ln(4e/√((t/b)²+(t/πW)²))
Z₀ = (60/√εr)·ln(4b/(0.67π·We·(0.8+t/We)))
εeff = εr (homogeneous — exact)
λ = 3×10¹¹ / (f[Hz]·√εr) mm
Offset: b_eff = 2·min(d, b−d)
αd = 27.3·√εr·tanδ / λ₀[m] dB/m
Rs = √(πfμ₀/σ) [Ω/sq]
αc = Rs/(Z₀·We) [Wheeler] Np/m
δs = 1/√(πfμ₀σ) [μm]
Np/m × 8.686/100 = dB/cm
About the Stripline Calculator
Stripline is a transmission line where the signal trace is buried between two ground planes inside a PCB stackup. Unlike microstrip, the trace is completely surrounded by the dielectric material, which means the effective permittivity equals the substrate permittivity exactly — making stripline more predictable and offering better EMC performance than microstrip.
Symmetric vs Offset Stripline
Symmetric stripline places the trace exactly at the centre between the two ground planes. Offset stripline places the trace closer to one ground plane. The impedance of offset stripline is calculated by finding an equivalent symmetric spacing using b_eff = 2·min(d, b−d).
When to Use Stripline
Stripline is preferred for high-speed digital signals above 5 GHz, clock distribution, and any signal where radiation or EMC is a concern. The two surrounding ground planes provide natural shielding. The tradeoff is higher dielectric loss compared to microstrip because the entire field is in the lossy dielectric with no air component.
PCB Design Guidelines
For a typical FR4 board targeting 50 Ω controlled impedance, a symmetric stripline with b = 3.2 mm requires a trace width of approximately 1.8 mm. Trace thickness for inner layers is typically 35 μm (1 oz copper).