📡 PCB Impedance Calculator
Calculate characteristic impedance for common PCB transmission line structures. Based on IPC-2141A and Wadell formulae.
Substrate Presets
FR4 (4.5)
FR4 @ 1GHz (4.3)
Rogers 4003C (3.55)
Rogers 4350B (3.48)
RO3003 (3.0)
PTFE (2.2)
Alumina (9.8)
Microstrip
Embedded Microstrip
Stripline (symmetric)
Differential Microstrip
Differential Stripline
Microstrip
Ground Plane
Trace (W)
Dielectric (εr)
H
W
Trace on top of dielectric, ground plane below.
Used for outer-layer signal routing.
$$Z_0 = \dfrac{87}{\sqrt{\varepsilon_r+1.41}}\ln\!\left(\dfrac{5.98H}{0.8W+T}\right)$$
⚠ Enter positive values for W, H, and εr.
Calculate
Clear
Embedded Microstrip
Trace is covered by a dielectric layer above (e.g. soldermask or prepreg). Ground plane below.
$$\varepsilon_{r,\text{eff}} = \varepsilon_r\!\left(1 - e^{-1.55\,B/H}\right)$$
$$Z_0 = \dfrac{87}{\sqrt{\varepsilon_{r,\text{eff}}+1.41}}\ln\!\left(\dfrac{5.98H}{0.8W+T}\right)$$
⚠ Enter positive values for all fields.
Calculate
Clear
Stripline (Symmetric)
Trace is embedded between two ground planes, centred in the dielectric. \(B\) = distance between ground planes.
$$Z_0 = \dfrac{60}{\sqrt{\varepsilon_r}}\ln\!\left(\dfrac{4B}{0.67\pi\,(0.8W+T)}\right)$$
⚠ Enter positive values for all fields.
Calculate
Clear
Differential Pair — Microstrip
Two coupled microstrip traces. Differential impedance is the impedance seen between the two conductors. \(Z_0\) is the single-ended microstrip impedance.
$$Z_\text{diff} \approx 2Z_0\!\left(1 - 0.347\,e^{-2.9\,S/H}\right)$$
⚠ Enter positive values for all fields.
Calculate
Clear
Differential Pair — Stripline
Two coupled traces embedded between ground planes. \(Z_0\) is the single-ended stripline impedance.
$$Z_\text{diff} \approx 2Z_0\!\left(1 - 0.347\,e^{-2.9\,S/B}\right)$$
⚠ Enter positive values for all fields.
Calculate
Clear
Common Target Impedances
Protocol / Use Z (single-ended) Zdiff
General signal 50 Ω — USB 2.0 — 90 Ω USB 3.x / USB4 — 85–90 Ω HDMI / DisplayPort — 100 Ω PCIe — 85 Ω Ethernet (100M/1G) — 100 Ω DDR memory (data) 40–60 Ω — RF / microwave coax 50 Ω — Video / 75 Ω systems 75 Ω — RS-422 / RS-485 — 120 Ω CAN bus — 120 Ω