Full-Time Equivalent (FTE) Calculations (Column Y): Insert the total number of hours worked by all part-time. and seasonal employees (all employees who did not work on average 30 or more hours per week per month. during the previous year). Divide each monthly total by 120 as a proxy of a 30 hour work week. (e.g., 240 hours worked in January/120 = 2) NOTE: the IRS has stated “the employer has the flexibility to determine the months in which the standard. measurement period starts and ends, provided that the determination must be made on a uniform and.