clock tree design

Hi,

We are designing a basic clock tree for a chain of flip-flops. The method that we are using is logic effort. Since the clock tree is just a bunch of inverters, G=1. So we only need to find out H (electrical effort), which is equal to Cout/Cin.

Here, Cout is the input capacitance of the flip-flop, which could be derived from the faundry's technology documents. But how to find out Cin. Is this equal to the pad's capacitance? If yes, how large is this and where to find out the value?

 Thanks a lot.