This PCB differential impedance calculator estimates the differential impedance of a coupled microstrip pair from the single-ended impedance, trace spacing, and height. Enter the values above.
Formula (coupled microstrip)
Zdiff ≈ 2 × Z₀ × (1 − 0.48 × e−0.96·s/h)
- Z₀ — single-ended impedance, s — edge spacing, h — dielectric height
Example
Z₀ = 50 Ω, s = 0.2 mm, h = 0.2 mm: Zdiff ≈ 81.6 Ω.
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Frequently Asked Questions
What is differential impedance?
It is the impedance a signal sees between the two traces of a differential pair, used for USB, HDMI, and Ethernet routing.
How do I get 100-ohm differential?
Bring the traces closer or narrow them so the coupled pair reaches 100 ohms differential, a common target.
Does spacing affect differential impedance?
Yes. Tighter spacing increases coupling and lowers the differential impedance.