29 C.F.R. § 541.104 : Labor — REGULATIONS RELATING TO LABOR — WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR — REGULATIONS — DEFINING AND DELIMITING THE EXEMPTIONS FOR EXECUTIVE, ADMINISTRATIVE, PROFESSIONAL, COMPUTER AND OUTSIDE SALES EMPLOYEES — EXECUTIVE EMPLOYEES — Two or more other employees

(a) To qualify as an exempt executive under §541.100, the employee must customarily and regularly direct the work of two or more other employees. The phrase "two or more other employees" means two full-time employees or their equivalent. One full-time and two half-time employees, for example, are equivalent to two full-time employees. Four half-time employees are also equivalent.
(b) The supervision can be distributed among two, three or more employees, but each such employee must customarily and regularly direct the work of two or more other full-time employees or the equivalent. Thus, for example, a department with five full-time nonexempt workers may have up to two exempt supervisors if each such supervisor customarily and regularly directs the work of two of those workers.
(c) An employee who merely assists the manager of a particular department and supervises two or more employees only in the actual manager's absence does not meet this requirement.
(d) Hours worked by an employee cannot be credited more than once for different executives. Thus, a shared responsibility for the supervision of the same two employees in the same department does not satisfy this requirement. However, a full-time employee who works four hours for one supervisor and four hours for a different supervisor, for example, can be credited as a half-time employee for both supervisors.

29 C.F.R. §541.104