How to estimate the size of the database that need to be backup? I read some reference that the size is about 2.5*content database. How about the backup size using back-spfarm? Is there any compression when backup as bak files? How to set the compression ratio? So, is the full backup size calculated as 2.5*content database*compress ratio? And what is the differential backup size estimation? Overall, I need to plan the space required for a weekly full and 5-6 differential backup. Thanks for providing any ideas that I am not clear.

Hi, File size of back up spfarm sharepoint almost 1 to 1.5 X from you db. (i.e if database size is 1 gb, back up file is 1.3 gb.)

Is this reference ok? http://www.sharepointsharon.com/2010/09/sizing-pt2-databases/ Can I just use the formula to estimate the content database size and then X 1.3 to get the backup file size?

I didnt read this article before. I get estimation size when backup my site collection with spfarm(with powershell).