Oracle Schema size

You can run the following SQL as SYS or SYSTEM account, to get all the schemas in the database and its size.

select owner, size_byte, round(size_byte/1024/1024,3) size_mb, round(size_byte/1024/1024/1024,3) size_gb,
u.account_status, u.created
from (  select owner, sum(bytes)  size_byte
        from dba_segments
        where owner not in ('SYS','APEX_030200','CTXSYS','DBSNMP','EXFSYS','MDSYS','OLAPSYS','ORDDATA','ORDSYS','OUTLN','SYSMAN','SYSTEM','WMSYS','XDB')
        group by owner
     ) z, dba_users u
where z.owner = u.username
order by 1