I'm trying to estimate SIZE parameter which can be specified during cluster definition. So I want to define cluster with only one attribute name varchar2(40) and add a table to this cluster. Average row length in this table is 29 bytes.

The disk block size is: 4096 bytes so the estimated number of bytes required
by an average cluster key and its associated rows is:

floor(disk_block/avg) = floor(4096/29) = floor(141,24) = 141 bytes.

Note that for each cluster key (name) we will have only one associated

Am I going the right way or is this a complete non-sense ?
In case I'm wrong - how can I estimate the SIZE attribute ?

thank you,