You'd need to define a target (over) pitching rate to be able to say. Assuming 1.2 million/mL-°P and 20 billion cells per gram, it would be ~3.6 grams per gallon.
The wrinkle there (apart from assuming cell density for the dried yeast) is that without a count you won't know viability for the non-rehydrated dry yeast. You could assume 50% loss from pitching dry, but those assumptions really start to compound at some point.