When calculating overtime under the FLSA, employers are required to pay employees an overtime rate of one and a half times their regular rate for all hours worked in a workweek in excess of 40, unless the employee is otherwise exempt. 29 USC 207.
A workweek consists of seven consecutive 24-hour periods that equal 168 total hours. An employer may choose to begin a workweek on any day of the week and there may be one defined workweek for all employees or different workweeks for different groups of employees or individual employees.
A nonovertime workweek is one where an employee works no more than 40 hours, and thus, is not entitled to be paid overtime under the FLSA. 29 CFR 778.101.
Establishing the start date of a workweek
An employer may choose the day of the week a workweek will begin. When an employer establishes a workweek, the workweek typically must remain fixed. However, it may be moved so long as the employer intends the change to be permanent and is not attempting to avoid paying overtime. 29 CFR 778.105; 29 CFR 778.301; 29 CFR 778.302.
Hours worked in a workweek determine whether overtime pay is required
All hours worked in one workweek are totaled to determine whether or not overtime pay is required. If an employee works 40 or fewer hours in a workweek, an employer is not required to pay overtime; if an employee works more than 40 hours in a workweek, an employer must pay overtime, unless the employee is exempt. Even if an employee works on more than one assignment, or works for two or more joint employers, overtime must be paid if more than 40 total hours are worked, unless an exemption applies. 29 CFR 778.103; see also 29 CFR 785.
Each Workweek stands alone
Whether an employer must pay an employee overtime is determined by each individual workweek. Workweeks cannot be averaged. For example, if an employee works 30 hours one week and 50 hours the next, the employee must be paid overtime for the 50 hour week even though the average between the two weeks is 40 hours a week. For purposes of determining overtime, employee hours must be calculated every week whether employees work varying shifts or whether the employees are paid weekly, monthly, annually, by salary, commission, piecework, or a flat rate. 29 CFR 778.104.