Stripline Impedance
Z0 = (60/√εr) × ln(4h/(0.67π×(0.8w+t)))
Quick answer
This calculator solves Z0 = (60/√εr) × ln(4h / (0.67π × (0.8w + t))) for Z0. With Dielectric Constant εr 5, Dielectric Height (mm) 100 mm, Trace Width (mm) 47 mm, Copper Thickness (mm) 22 mm, the result is 31.11 Ω.
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Formula
Description
A stripline is a transmission line embedded between two ground planes inside the PCB stackup. Unlike microstrip which has dielectric on one side and air on the other, stripline is fully surrounded by dielectric, resulting in a homogeneous propagation medium with well-controlled impedance and lower radiation. Stripline impedance depends on the dielectric constant, the distance between ground planes, and the trace geometry. Stripline routing is preferred for sensitive high-speed signals because the ground planes provide excellent shielding from external noise and minimize crosstalk.
Variables
- Z0 — Characteristic impedance (Ω)
- εr — Relative dielectric constant
- h — Total distance between ground planes (mm)
- w — Trace width (mm)
- t — Copper thickness (mm)
Practical Notes
Stripline has about 40% lower propagation velocity than microstrip due to being fully immersed in dielectric. For FR-4 with εr = 4.2, a 50Ω stripline requires a wider trace than a 50Ω microstrip for the same dielectric thickness. Dual stripline uses two signal layers between three ground planes to increase routing density. Consult your PCB fab stackup data for accurate εr values.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| er | Dielectric Constant εr | — | — |
| h | Dielectric Height (mm) | mm | mm |
| w | Trace Width (mm) | mm | mm |
| t | Copper Thickness (mm) | mm | mm |
Step by step
- 1. What you know: Dielectric Constant εr 5, Dielectric Height (mm) 100 mm, Trace Width (mm) 47 mm, Copper Thickness (mm) 22 mm
- 2. The relation: Z0 = (60/√εr) × ln(4h / (0.67π × (0.8w + t)))
- 3. Substitute: er = 5, h = 100 mm, w = 47 mm, t = 22 mm
- 4. Result: Z0 = 31.11 Ω
Worked examples
Minimum range
Given: Dielectric Constant εr 0.25, Dielectric Height (mm) 1 mm, Trace Width (mm) 0.47 mm, Copper Thickness (mm) 0.22 mm
Result: Z0 = 139.1 Ω
Low range
Given: Dielectric Constant εr 2.5, Dielectric Height (mm) 10 mm, Trace Width (mm) 4.7 mm, Copper Thickness (mm) 2.2 mm
Result: Z0 = 44 Ω
Typical
Given: Dielectric Constant εr 5, Dielectric Height (mm) 100 mm, Trace Width (mm) 47 mm, Copper Thickness (mm) 22 mm
Result: Z0 = 31.11 Ω
High range
Given: Dielectric Constant εr 8, Dielectric Height (mm) 1000 mm, Trace Width (mm) 470 mm, Copper Thickness (mm) 220 mm
Result: Z0 = 24.6 Ω
Maximum range
Given: Dielectric Constant εr 80, Dielectric Height (mm) 10000 mm, Trace Width (mm) 4700 mm, Copper Thickness (mm) 2200 mm
Result: Z0 = 7.779 Ω
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<p><a href="https://vbatpower.com/formulas/stripline-impedance/">Stripline Impedance</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Stripline Impedance?
Use Z0 = (60/√εr) × ln(4h / (0.67π × (0.8w + t))). With Dielectric Constant εr 5, Dielectric Height (mm) 100 mm, Trace Width (mm) 47 mm, Copper Thickness (mm) 22 mm, Z0 works out to 31.11 Ω.
What is the formula for Stripline Impedance?
The formula is Z0 = (60/√εr) × ln(4h / (0.67π × (0.8w + t))). A stripline is a transmission line embedded between two ground planes inside the PCB stackup.
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