Your answer depends on a few things:
1. The count
2. The number of decks
3. The rules
In general, the equation is CV = Vn + .5(n-1)
I think that is correct. n is the number of hands (in your case 2), and V is the variance according to the above criteria. Go to bjstats.com to find the specific variance you want. Usually the figure is between 1.13 and 1.3.