Factors that affect the choice of Span of control?

There are two main factors that impact the ideal span of control (number of direct reports) for a manager:

1) How much non-supervisory work the manager is expected to do himself / herself. This then determines how much capacity he has to supervise subordinates. The more work a manager must do, the smaller his span of control should be.

2) How much effort is required to supervise each subordinate. For example, if it does not require much time each week to supervise a certain type of subordinate, the manager's span of control can be greater. This will vary across the different functions in a business.