Signal Integrity Crosstalk Calculator

Work out signal integrity crosstalk instantly with clear inputs, formula shown and shareable results.

About Signal Integrity Crosstalk Calculator

Crosstalk falls roughly as 1/(1 + (S/H) squared), which is the basis of the 3W rule: spacing three times the trace width, or about three times the dielectric height, cuts coupling to a few percent. Backward crosstalk saturates once the coupled length exceeds half the rise-time length.

Formula

Crosstalk

Kb approx 0.5 / (1 + (S/H)^2); saturation length = rise time x propagation velocity / 2

Worked example

With the default values below, Signal Integrity Crosstalk Calculator returns Backward crosstalk coefficient of 15.385%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Trace spacing: 0.15 mm
Height above the reference plane: 0.1 mm
Coupled length: 25 mm
Signal rise time: 100 ps

Results

Backward crosstalk coefficient: 15.385% %
Spacing to height ratio: 1.50 x
Saturation length: 7.50 mm
Assessment: Too close - expect significant crosstalk

Step by step

1Values used
2Crosstalk
3Backward crosstalk coefficient= 15.385 %
4Spacing to height ratio= 1.50 x
5Saturation length= 7.50 mm
6Assessment= Too close - expect significant crosstalk

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What is the 3W rule?

Keep centre-to-centre spacing at least three times the trace width. It is a proxy for the spacing-to-height ratio that actually governs coupling.

Why does backward crosstalk saturate?

Once the coupled length exceeds half the rise-time length, additional coupling arrives after the reverse wave has already reached its peak, so the amplitude stops growing.