On its surface, employee turnover may look like attrition since it occurs when an employee leaves his or her job. But in this case, the vacancy must be filled. A company’s turnover rate can be determined by dividing the number of departing employees by all the employees for a specified period. For example, calculating the turnover rate for a year might look like this: two employees departing divided by 10 total employees equals 0.2. That gives a turnover rate of 20%.