oracle size of database

select

    a.tablespace_name

    , total

    , free

    , total - free as used

    , substr(free / total * 100, 1, 5) as "FREE%"

    , substr((total - free) / total * 100, 1, 5) as "USED%" 

from

    ( 

        select

            tablespace_name

            , sum(bytes) / 1024 / 1024 as total 

        from

            dba_data_files 

        group by

            tablespace_name

    ) a

    , ( 

        select

            tablespace_name

            , sum(bytes) / 1024 / 1024 as free 

        from

            dba_free_space 

        group by

            tablespace_name

    ) b 

where

    a.tablespace_name = b.tablespace_name 

order by

    a.tablespace_name;