Dear Pranothi,
Manpower planning varies from one industry to another and one company to another.
Let me give you simple example. I am given to understand that Oberoi Group (hospitality sector) follows 1:2.5 ratio i.e. for every hotel room there should be 2.5 persons. This includes security, gardener, gym asst to G.M of the hotel. However, others do not follow the same principle.
Manpower planning is based on the standards of your industry. First find out those standards, then your job will become easy. While doing manpower planning, you need to take into account absence of employees because of leave (as per the statute), their sickness, attrition etc. Many companies do not make any provision for their valid or invalid absence. In the bargain other employees end up in working more. This is the starting point of down-slide of morale and motivation.
The second practice is to take some manpower on higher side. Later as and when attrition happens, you need not fill those vacancies.
Ok...
Dinesh V Divekar