Script to find the tablespace usage

select df.tablespace_name "Tablespace",
 totalusedspace "Used MB",
 (df.totalspace - tu.totalusedspace) "Free MB",
 df.totalspace "Total MB",
 round(100 * ( (df.totalspace - tu.totalusedspace)/ df.totalspace))
 "Pct. Free"
 from
 (select tablespace_name,
 round(sum(bytes) / 1048576) TotalSpace
 from dba_data_files
 group by tablespace_name) df,
 (select round(sum(bytes)/(1024*1024)) totalusedspace, tablespace_name
 from dba_segments
 group by tablespace_name) tu
 where df.tablespace_name = tu.tablespace_name ;