E.05Microstrip Impedance Calculator
Calculate impedance from trace width, or find the width needed for a target impedance.
Results
- Impedance Z₀
- —
- Trace width
- —
- εeff
- —
- Delay
- —
- W / H
- —
Formulas
- Method
- Hammerstad & Jensen (1980), with thickness correction
- Delay
- t_pd = √εeff / c
Assumptions
The calculation is for an uncoated surface microstrip over a single reference plane; solder mask typically lowers impedance by 1–3 Ω. Dispersion is not included; below a few GHz results are typically accurate to 1–2%.
Verify against your PCB manufacturer’s stack-up and controlled-impedance data before production.
References
- E. Hammerstad, Ø. Jensen, “Accurate Models for Microstrip Computer-Aided Design”, IEEE MTT-S, 1980
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