An important component of managerial leverage is the number of subordinates a manager has. If he does not have enough, his leverage is obviously reduced. If he has had many, he gets bogged down-with the same result. As a rule of thumb, a manager whose work is largely supervisory should have 6 to 8 subordinates; 3 or 4 are too few and 10 are too many. This range comes from a guideline that a manager should allocate about a half day per week to each of his subordinates.
(Two days a week per subordinate would probably lead to micromanagement and an hour a week does not provide enough opportunity for monitoring and coaching .)
What about a know-how manager
The middle manager who mainly supplies expertise and information. Even if he works without a single subordinate, servicing a number of varied “customers” as an internal consultant/expert can in itself be a full-time job. In fact, anyone who spends about a half day per week as a member of a planning, advisory, or coordinating group has the equivalent of a subordinate. So as a rule of thumb again, if a manager is both a hierarchical supervisor and a supplier of know-how, he should try to have a total of six to eight subordinates or their equivalent.