Help in table size estimation

[dinesh_hm]

Hi,
I want to do a proper table size estimation
and Iam using the following formula to do it

Expected size (MB)= (( RS * number of rows) / AVIL ) * OBS) / 2048

Where RS = Average row size
AVIL= Available space in each db block
OBS =DB block size

However after creating the object when i query the dba_segments
by taking sum(bytes) in MB the size is almost half the actual estimation done by the earlier formula

Is there any other accurate way of verifying the exact size after creating the table ?

[PAVB]

http://www.arikaplan.com/oracle/ari32999.html