Impedance calculator.

Sanity-check your single-ended and differential impedance before sending Gerber to fab. Same math we use on every stack-up quote — no sign-up, no wait.

Use the calculator About impedance control

Common targets

50 ΩSingle-ended · clock · RF
90 ΩUSB 2.0 differential
100 ΩUSB 3 · PCIe · LVDS · DDR

Under the Hood

Same math we run on every order

Hammerstad–Jensen for microstrip, parallel-plate with edge correction for stripline. Differential pairs use Polar-style odd-mode analysis. Tolerances tied to IPC-6012 class spec.

Microstrip

Z₀ ≈ 87 / √(Dk + 1.41) · ln(5.98 × H / (0.8W + T))

Signal layer · outer reference plane

Stripline

Z₀ ≈ 60 / √Dk · ln(4 × B / (0.67 π × (0.8W + T)))

Buried signal · two reference planes

Differential

Z_diff ≈ 2 × Z₀ × (1 − 0.48 × e^(−0.96 × S/H))

Odd-mode · with coupling S/H

Standard

IPC-2141

Frequently Asked Questions

Impedance calculator FAQ

Ask a specialist

01How accurate is the calculator vs Polar Si9000?

For standard microstrip and stripline: typically within ±3% of Polar. For high-frequency (>5 GHz) or unusual stack-ups, we recommend Polar for the final sign-off.

02Does Dk vary with frequency?

Yes — significantly. FR-4 Dk typically drops from ~4.5 @ 1 MHz to ~4.2 @ 5 GHz. Enter the Dk for your target frequency, not the datasheet nominal.

03Can I use this for via impedance?

Not directly — vias are 3D structures best simulated in a full-wave solver (HFSS, ADS). Use this tool for traces; we can help with via simulation on request.

04Do you offer other calculators?

Yes — browse the full list: trace width (IPC-2152), voltage drop, conduit fill, wire gauge, and more.

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