As an Administrator, you will see a percentage value for your companies staff turnover within your dashboard.

Below is the calculation used for this percentage. Please note that this figure is calculated on a rolling 12 month period:
Leavers (in the last 12 months) / (current employees + Leavers (in the last 12 months)) x 100.
If you wish to calculate this for a different period of time, you can simply create 2 queries, 1 filtering on leavers with a specific time frame and the 2nd query providing you with the number of current active employees.
The below articles may be useful in creating these:
http://help.peoplehr.com/reporting-and-queries/creating-queries
http://help.peoplehr.com/reporting-and-queries/filter-a-query-by-a-specific-time-frame
Thanks,
Customer Service Team.