oracle table free space

select f.tname "TableSpace",
round(sum(d.bytes)/1024, 0) "Total(KByte)",
round((sum(d.bytes) - sum(f.bytes))/1024, 0) "UsedSpace(KByte)",
round((sum(d.bytes) - sum(f.bytes))/sum(d.bytes)*100, 0) "Used(%)",
round(sum(f.bytes)/1024, 0) "FreeSpace(KByte)"
from
(select sum(bytes) bytes,
tablespace_name tname
from dba_free_space
group by tablespace_name) f,
(select sum(bytes) bytes,
tablespace_name tname
from dba_data_files
group by tablespace_name) d
where f.tname = d.tname
group by f.tname