Simon Horman a écrit :

Surprisingly its a very common question amongst users,
because they want to know how much memory they need.
It is of course all a bit silly, because the amount of
memory used by the connection table is usually very small,
but people still ask.

If SLUB is used 

$ cat /sys/kernel/slab/ip_vs_conn/object_size

If SLAB is used, take fourth column of :

$ grep ip_vs_conn /proc/slabinfo

BTW these take into account L1 cache size alignment