lync 2013 bandwidt required for video call

I used below url, is my calculation correct 

http://technet.microsoft.com/en-us/library/jj688118(v=ocs.15).aspx  <o:p></o:p>

 for Main video when calling Lync 2013 endpoints,  codec H.264, typical stream bandwidth 460 kbps <o:p></o:p>

so for 300 users,    460* 300  = 138000 kbps = 138000/8 KBPS =  17250 KBPS = 16 mbps<o:p></o:p>

is my calculation correct.

i also need calculation for HD video call, where is the info for that, is there any calculator i can use for the same.

also what is the minimum bandwidth required for IM/presence?