calculating size of a table

[Vipassana]

select avg_row_len * num_rows * (1 + PCT_FREE/100) * 1.15
from dba_tables where table_name = 'PRODUCT'
/

AVG_ROW_LEN*NUM_ROWS*(1+PCT_FREE/100)*1.15
------------------------------------------
13925.12

SQL> select sum(bytes) from user_segments where segment_name = 'PRODUCT';

SUM(BYTES)
----------
65536