I am far from your neck of the woods but, in addition to the good input you have already received, here are a couple of thoughts: Talk with your county extension agent. There are so many variables to consider. Breed of cattle, weather patterns, quality of pasture in the summer months, and so forth. Do you have a good pasture mix of grass and legumes growing? Personally, I do not like to figure out a maximum number; I like having a cushion of sorts and Lord knows lack of rain alone can mess up your math. If forced to spit out a general formula, I'd probably say 2 acres per adult cow. I tend to be conservative about things. Your county agent and local folks who have good looking cattle (and good looking pasture in late summer) are worth listening to. Good luck.