Attrition formula - I am bit confused

I generate MIS report and in which we need to put attrition formula but I am bit confused in it.
Attrition Rate = ((No. of Exit x 100) / (Opening Balance + No. of New Joining) / 100))
Kindly check it and let me know that it is right or wrong.

Please keep in mind that while calculating Attrition, we have to take into consideration only Employees who have left organisation on their own. Employees who are Desired Separations or who were asked to quit the organisation should not be considered in your Attrition Rate.
Hence the formula can be as mentioned below :
Attrition Rate = Total No. of employees left on their own/Opening balance of manpower at the start of period + new additions during the period + transfers in the division/department * 100

Attrition Rate: Total No. of left / Opening balance*100
Regards
Balaji