Differential Pair Impedance Calculator
Estimate differential impedance for microstrip and stripline pairs using trace geometry, spacing, and dielectric inputs.
Differential Pair Impedance Calculator
Estimate differential pair impedance for high-speed PCB routing, then use the result as an early stackup and fabrication review reference.
Typically 4.2-4.6 for FR4
1oz Cu ≈ 0.035mm
Microstrip
When to use this calculator
Use it for USB, Ethernet, LVDS, PCIe, HDMI, and other differential routing where pair geometry strongly affects signal quality.
Check whether your spacing and trace geometry are directionally close to the target pair impedance before final fabrication review.
Use it together with stackup planning and material review when discussing controlled differential routing with your PCB manufacturer.
Practical notes
• Differential impedance depends on both single-ended geometry and pair coupling.
• Spacing, dielectric thickness, copper thickness, and etching all affect the final result.
• Controlled differential pairs should always be finalized against the real fabrication stackup.
Related resources & next steps
Cross-check single-ended impedance assumptions before finalizing differential pair geometry.
Use a preliminary stackup plan to frame spacing, dielectric, and pair-routing constraints.
Review dielectric assumptions before relying on pair impedance estimates.
Move from estimated pair impedance to a fabrication-ready differential routing review.
Send your target differential impedance, stackup assumptions, and routing constraints to engineering.
Frequently Asked Questions
What differential impedance target is most common?
100Ω differential is the most common target for many high-speed digital interfaces, but some interfaces and stackups use different values. Always confirm the target from your design rules and manufacturer requirements.
Why can the differential result change so much with spacing?
Because spacing changes electromagnetic coupling between the two traces. Tighter spacing increases coupling and changes the pair’s overall differential impedance.
Is this enough for production release?
No. Treat it as an engineering estimate. Final differential pair rules should be validated against the actual stackup, laminate data, and fabrication tolerances from your PCB manufacturer.
Need help turning a target differential pair into a manufacturable routing rule?
We can help review stackup assumptions, trace geometry, dielectric choices, and controlled impedance feasibility before fabrication.