PCB Trace Impedance Calculator

Calculates the characteristic impedance and per-unit-length parameters of typical printed circuit board trace geometries.

Select a configuration:

Microstrip Trace

Embedded Microstrip Trace

Stripline Trace

Asymmetric Stripline Trace

Geometric Parameter Definitions

W: trace width

T: trace thickness

H (/H1) height of trace or dielectric above return plane

C: distance between the differential stripline pair

er: relative permittivity of the dielectric

Electrical Parameter Definitions

Zo: characteristic impedance

Zc: effective characteristic impedance including the capacitance of distributed loads

Tpd: propagation delay

Lo: inductance per unit length

Co: capacitance per unit length

Acknowledgements:

The source for formulas used in this calculator (except where otherwise noted) is:
IPC-D-317A, Design Guidelines for Electronic Packaging Utilizing High-Speed Techniques, Jan 1995; Section 5, pp. 13 - 36.

THESE FORMULAS ARE APPROXIMATIONS!
They should not be used when a high degree of accuracy is required.

The transmission line calculator concept was developed by Douglas Brooks and is described in his paper: PCB Impedance Control: Formulas and Resources, Printed Circuit Design Magazine, March 1998. A copy of his paper and a similar transmission line calculator that runs on a PC can be obtained from UltraCAD Design, Inc.