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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
Microstrip Trace
Embedded microstrip trace
Embedded Microstrip Trace
Stripline Trace
Stripline Trace
Asymmetric 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


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.

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.