DBA_FREE_SPACE

Columns
   ___________________________
 
   TABLESPACE_NAME
      Name of the tablespace containing the extent
   FILE_ID
      ID number of the file containing the extent
   BLOCK_ID
      Starting block number of the extent 
   BYTES
      Size of the extent in bytes
   BLOCKS
      Size of the extent in ORACLE blocks
   RELATIVE_FNO
      Relative number of the file containing the extent

SELECT tablespace_name ,sum(bytes)/1024/1024 "MB Free"
FROM dba_free_space
WHERE tablespace_name <>'TEMP'
GROUP BY tablespace_name;

Related: