HOW TO ESTIMATE THE SIZE OF A TABLE IN BYTES IN ORACLE

To find the size of bytes allocated to a table:

sql > analyze table emp compute statistics;

sql > select num_rows * avg_row_len "Bytes Used" from dba_tables where table_name = 'TEST';

Bytes Used
-----------
560

sql > select bytes "Bytes Allocated" from dba_segments where segment_name = 'TEST';


Bytes Allocated
----------
524288

The result of the query shows that the emp table is using 560 bytes of the 524,288 bytes allocated to it.