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PCB Microstrip Impedance Estimate — result sheet
Estimate the characteristic impedance of a single-ended microstrip from dielectric constant, trace geometry, and reference-plane height.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: Z₀ ≈ [60/√(0.475εr+0.67)] ln[4h/(0.67(0.8w+t))] for the stated microstrip approximation.
Controlled impedance is a geometry-and-material problem, not just a trace-width label. This compact estimate exposes the reference-plane height, dielectric constant, width, and copper thickness so a board designer can use it as a starting point before field-solver or fabricator verification.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Relative permittivity εr — minimum 1.0E-6; maximum 1000
- Trace-to-plane height — mm; minimum 1.0E-6; maximum 1000000
- Trace width — mm; minimum 1.0E-6; maximum 1000000
- Trace thickness — mm; minimum 0; maximum 1000000
Worked example
| Input | Value |
|---|---|
| Relative permittivity εr | 4.2 |
| Trace-to-plane height | 0.2 |
| Trace width | 0.3 |
| Trace thickness | 0.035 |
Estimated single-ended microstrip impedance ≈ 51.8 Ω.
Assumptions and limits
- The trace is a single-ended microstrip above a nearby reference plane with homogeneous effective dielectric behavior.
- All geometry inputs use the same length unit; the logarithm uses the stated approximation's positive geometry ratio.
- Solder mask, dispersion, copper roughness, frequency, differential coupling, vias, connectors, and fabrication tolerances are not modeled.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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