Get tablespaces usage

SELECT t1.TABLESPACE_NAME AS "Tablespace Name",
 t1.BYTES AS "Bytes Used",
 t2.BYTES AS "Bytes Free",
 t2.largest AS "Largest",
 ROUND(((t1.BYTES - t2.BYTES)/t1.BYTES)*100,2) AS "% Used"
FROM
 (
  SELECT TABLESPACE_NAME,
   SUM(BYTES) BYTES
  FROM  dba_data_files
  GROUP BY TABLESPACE_NAME
 ) t1,
 (
  SELECT TABLESPACE_NAME,
   SUM(BYTES) BYTES ,
   MAX(BYTES) largest
  FROM  dba_free_space
  GROUP BY TABLESPACE_NAME
 ) t2
WHERE  t1.TABLESPACE_NAME = t2.TABLESPACE_NAME
ORDER BY ((t1.BYTES - t2.BYTES)/t1.BYTES) DESC