Hi amarprsi,
The buffer capacity usually depends on the type of the line card. By default the buffer capacity is 100ms for ports 1g and higher for an Ethernet port which is distributed to the queues configured on that port. Few of the newer line card also support 250ms as well.
Just to give you an instance:
Calculation for a single 10gig port with default config is 125MB
100ms for interface (125MByte)=(100/1000)*10*1000000000/8
[KUDOS PLEASE! If you think I earned it!
If this solution worked for you please flag my post as an "Accepted Solution" so others can benefit..]