You wouldn't mean figuring things out has something to do with reasoning, would you? We all need to become more mathematically minded so we can have this discussion. What do we have to work with? How much land? What are the resources? What is the size of the population that live within these limits?
From there, once it's determine what kind of residential areas, single family homes, townhouses, apartments, condominiums, schools, healthcare facilities, etc. can be supported, then maybe an estimate can be made on the population capacity. But let me ask you this, has anyone ever asked what the population capacity for any town or city would be, before they were created? Did someone ask what would the population capacity be for Las Vegas, before it went from plain desert to a large populated city? Why does such a question need to be asked?