oracle tablespace Total free space

SELECT
    SUBSTR(a.tablespace_name,1,30) TABLESPACE,
    ROUND(SUM(a.total1)       /1024/1024,1) "TotalMB",
    ROUND(SUM(a.total1)       /1024/1024,1)-ROUND(SUM(a.sum1)/1024/1024,1) "UsedMB",
    ROUND(SUM(a.sum1)         /1024/1024,1) "FreeMB",
    ROUND((ROUND(SUM(a.total1)/1024/1024,1)-ROUND(SUM(a.sum1)/1024/1024,1))/ROUND(SUM(a.total1)/1024/1024,1)*100,2) "Used%"
  FROM
      (
      SELECT tablespace_name,
             0 total1,
             SUM(bytes) sum1,
             MAX(bytes) MAXB,
             COUNT(bytes) cnt
        FROM dba_free_space
       GROUP BY tablespace_name
      UNION
      SELECT tablespace_name,
             SUM(bytes) total1,
             0,
             0,
             0
      FROM dba_data_files
      GROUP BY tablespace_name
      ) a
GROUP BY a.tablespace_name
ORDER BY TABLESPACE;