Oracle: check real table size on disk

SELECT
   owner, table_name, TRUNC(sum(bytes)/1024/1024) Meg
FROM
(SELECT segment_name table_name, owner, bytes
 FROM dba_segments
 WHERE segment_type = 'TABLE'
 UNION ALL
 SELECT i.table_name, i.owner, s.bytes
 FROM dba_indexes i, dba_segments s
 WHERE s.segment_name = i.index_name
 AND   s.owner = i.owner
 AND   s.segment_type = 'INDEX'
 UNION ALL
 SELECT l.table_name, l.owner, s.bytes
 FROM dba_lobs l, dba_segments s
 WHERE s.segment_name = l.segment_name
 AND   s.owner = l.owner
 AND   s.segment_type = 'LOBSEGMENT'
 UNION ALL
 SELECT l.table_name, l.owner, s.bytes
 FROM dba_lobs l, dba_segments s
 WHERE s.segment_name = l.index_name
 AND   s.owner = l.owner
 AND   s.segment_type = 'LOBINDEX')
WHERE owner in ('SCHEMA_NAME')
GROUP BY table_name, owner
HAVING SUM(bytes)/1024/1024 > 10  /* Ignore really small tables */
ORDER BY SUM(bytes) desc ;