Exchange 2007 Mailbox Server Role Storage Requirements Calculator v15.6
Ross Smith IV announced at the Microsoft Exchange Team Blog that the Exchange 2007 Mailbox Server Role Storage Requirements Calculator v15.6 has been released to the general public.
According to the updates tracking page at the You Had Me At EHLO blog, the changes include some bug fixes as well as some enhancements.
To get the detailed instructions on how to use it, read Exchange 2007 Mailbox Server Role Storage Requirements Calculator.