To determine a salary worker’s pay per pay period, divide the annual salary into the total yearly pay periods. For instance, say she earns $64,000, paid semimonthly. Calculation: $64,000 / 24 semimonthly pay periods = $2,666.67 (semimonthly salary). Related Reading: How to Calculate Bi-Monthly Payroll Salary.ay the hours according to the pay frequency. Suppose the employee earns $11 an hour, paid biweekly. His time card for two consecutive weeks reflects 40 hours worked. Regular calculation: 40 hours x 2 weeks = 80 hours x $11/hour = $880 (gross regular pay).