is there any way to find out how much tcp buffer currently linux handling? (kernel tunning)

Hi
i know w hich parameter change to tune tcp .. example

net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216


but what i want to know is :
is there any way you can see, or is there any statistics data in the system to find out.. how much tcp buffer it has used in a given time ??

example :
you increased your RAM to 20GB, and you can monitor the uses script.
so suppose your maximum tcp send buffer is 16MB

how will you know that when you  actually need to increase the size ??
or is there any way to know that how much RAM its actually using per connection ???

I know Application or oracle they say that you need to set certain amount of tcp buffer.
unless an application states..
how will you know the uses ??

hope it does make sense

thanks