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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. Compute Z0 from geometry or inverse solve for width for a particular Z0.

Units
Length
Frequency

Inputs

Mode?
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

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

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