How to calculate matching loss

I would like to know how much power is lost on matching network when you
design a matching.

Could anyone advise how to calculate matching loss?
Thanks a lot.

According to Joseph R White's "High Frequency Techniques", the

mismatch loss = 1 - (p)^2

where p is the Return loss.

Issit what you want to find?

I think mismatch loss is also equal to 1-S11*S11,you can use EDA tools display this.