To calulation ORACLE data guard / standby Bandwidth.

If you are building Oracle Datagaurd and if you want to find minimum estimated network bandwidth execute the below query in PR.

Select    Max(SizeOfFile) MaxSize,  
Avg(SizeOfFile) AvgSize,  
Ceil((Decode(Sign(Max(SizeOfFile)-5*Avg(SizeOfFile)),1,
Avg(SizeOfFile)*(1+0.25),   
Max(SizeOfFile)*(1+0.25))*8)/(3600*1024*1024)) BandWidth_Mbps
From
(Select to_char(COMPLETION_TIME,'YYYY-MON-DD HH24') Completion_Hour,
Sum(BLOCK_SIZE*(BLOCKS+1)) SizeOfFile
     From 
     V$ARCHIVED_LOG  where Dest_id = 1  Group By to_char(COMPLETION_TIME,'YYYY-MON-DD HH24'));