How to Check the table Size in Oracle.

To check table name segment type and table size in MB 

SQL> select segment_name,segment_type,bytes/1024/1024 MB from dba_segments where segment_type='TABLE' and segment_name='sujeet'

             SEGMENT_NAME         SEGMENT_TYPE                      MB

           -------------------- ------------------ ---------------------------------------

             sujeet                                 TABLE                                          192

To check Table Owner,Table Name and Table Size.

You can check here one SYSTEM owner have multiple tables with different sizes and names.

SQL> select owner,segment_name,sum(bytes)/1024/1024/1024 as "SIZE in GB" from dba_segments where owner='SYSTEM' and segment_type='TABLE' group by owner,segment_name order by                  "SIZE in GB" desc;

OWNER                          SEGMENT_NAME         SIZE in GB              

------------------------------ ---------------------------------------------------------------            

SYSTEM                                 SONU                  1.50683594              

SYSTEM                                 Aasu                  .984375              

SYSTEM                                BIHAR                   .921875      

SQL > select owner,segment_name,sum(bytes)/1024/1024/1024 as "SIZE in GB" from dba_segments

where owner='SCOT' and segment_type='TABLE' group by owner,segment_name order by "SIZE in GB" desc;

SQL >  select owner,segment_name,sum(bytes)/1024/1024/1024 as "SIZE in GB" from dba_segments

where owner='SCOT' and segment_type='LOBSEGMENT' group by owner,segment_name order by "SIZE in GB" desc;