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RayRF | Free RF calculators

Stripline Impedance Calculator (IPC-2141A)

Solve symmetric stripline characteristic impedance Z0 from geometry, or invert for the trace width that hits your target. IPC-2141A formulation with finite-thickness correction.

Stripline Calculator

Symmetric stripline, a trace buried between two ground planes. The trace is fully shielded, so radiation is low and impedance control is tight. Compute Z0 from geometry or solve for trace width to hit a controlled impedance target.

Units
Length
Frequency

Inputs

Ω
mm
GHz
W = 0.382 mmb = 1 mmεr = 3.66top groundbottom ground
Symmetric stripline
Characteristic impedance Z0
50.00Ω
Required width W
0.382mm
15.05 mil

More

Effective eeff3.660
Guided lambda_g27.018 mm
lambda_g / 46.754 mm

Analytical calculation

Every step the calculator runs, with the formula, your numbers plugged in, and the result.

Solve trace width
Invert the IPC-2141 stripline formula by bisection until it matches the target.
Effective width
Corrects for finite copper thickness t.
Characteristic impedance
IPC-2141 / Wadell. Symmetric stripline is homogeneous, so eeff = er exactly.
Guided wavelength
Homogeneous medium, so eeff = er.

Frequently asked

When should I use stripline instead of microstrip?

Stripline shields the trace between two grounds; almost no radiation, no soldermask sensitivity, and crosstalk is much lower. Use it for high-isolation feed networks and inner-layer routing.

What's the impedance of a 0.5 mm stripline on RO4350B?

For b = 1.0 mm, W = 0.5 mm, and 35 um copper on RO4350B (er = 3.66), the IPC-2141 closed form gives about 43 ohm. To hit 50 ohm on the same stackup, switch to Solve W and you will get about W = 0.38 mm. Note that W = 0.5 mm puts W/(b - t) above the IPC-2141 narrow-strip validity window (0.35); for wide traces, cross-check in a wide-strip table such as Wadell or in RayRF.

References

Closed-form is just the start.

These calculators hand you the analytical starting point. RayRF takes you the rest of the way: antennas, filters, feedlines, and more, simulated on your real stackup with copper losses, dielectric loss, and finite ground. Roughly a second per iteration.

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