Controlled Impedance Calculator

Microstrip, stripline and edge-coupled differential pair impedance from your stackup geometry, using the IPC-2141 closed-form expressions — plus the w/h ratio so you know whether the formula applies to your geometry at all.

Build the stackup →Dk / Df data →Quote the build →
Oscilloscope trace and probes measuring an impedance test coupon
±8%control tolerance
±8 µmwidth accuracy

Default values correspond to a common 4-layer stackup: 4.5 mil dielectric, 6 mil trace, 1 oz copper, 6 mil differential gap, FR-4 at Dk 4.3.

The formulas being used

Microstrip Z₀Z₀ = 87 / √(Dk + 1.41) × ln( 5.98h / (0.8w + t) )
Stripline Z₀Z₀ = 60 / √Dk × ln( 4h / (0.67π(0.8w + t)) )
Differential, edge-coupled microstripZₗₕₖₖ = 2Z₀( 1 − 0.48 e−0.96 s/h )
Differential, edge-coupled striplineZₗₕₖₖ = 2Z₀( 1 − 0.347 e−2.9 s/h )

All dimensions in the same unit. Valid for 0.1 < w/h < 2.0. These are the IPC-2141 closed-form approximations, accurate to roughly ±5% in range. Our own process holds ±8% impedance tolerance, verified with per-panel coupons when specified — see the quality page.

When to ask for a coupon instead

Ask us to build an impedance coupon into the panel when the target is within 10% of a critical value — USB 3.x, HDMI, PCIe Gen 4/5, DDR4/DDR5, or any RF feed. The coupon is measured on the finished panel and the report ships with the boards. It costs one additional setup, and it is the only way to know the impedance you actually received rather than the impedance you designed.