how to find size to table in oracle?

Question

in bytes

Answer 1

The size that the table is taking up in storage is found in the dba_segments, or user_segments view:
select segment_name,bytes from user_segments where segment_name = 'EMPLOYEE';

If you want the size of the data in the table, then the table has to be freshly analyzed and you can use the statistics that get populated into the DBA_TABLES or USER_TABLES view.
analyze table EMPLOYEE compute statistics;
select table_name, (num_rows * avg_row_len) from user_tables where table_name = 'EMPLOYEE';