Microstrip, Stripline, Coax and Differential Pair Impedance Calculator

Microstrip, stripline, coax and differential-pair impedance from geometry, with propagation delay and a width solver.

Structure Length unit Dielectric constant εr Trace width w Dielectric height to the plane h Copper thickness t Spacing between the pair s (edge to edge) Distance between the two planes b Inner diameter of the outer conductor D Diameter of the centre conductor d

Target impedance (Ω) — solve for width

Closed-form IPC-2141 style approximations: microstrip Z₀ = 87/√(εr + 1.41) · ln(5.98h / (0.8w + t)); stripline Z₀ = 60/√εr · ln(4b / (0.67π(0.8w + t))); coax Z₀ = 60/√εr · ln(D/d); differential: Z_diff = 2·Z₀·(1 − 0.48·e^(−0.96·s/h)) (microstrip), 2·Z₀·(1 − 0.347·e^(−2.9·s/b)) (stripline). Typical accuracy is several percent — use a field solver and your PCB fabricator’s stack-up for the final design.

For preliminary assessment only — the final decision must follow the manufacturer’s datasheet and the applicable NEC / IEC / UL standards. Results are calculated from the standard formulas stated on this page and are for design estimates only. They are not a rating of any specific part — always confirm current, voltage, temperature and environment limits against the manufacturer’s datasheet for the part you intend to use.

Need help with a connector?

Tell us what you are designing — our engineers can suggest series and second-source options.

← All tools