Query To Check Tablespace Allocated Size and Free Size in GB

Select b.tablespace_name, tbs_size SizeGB, a.free_space FreeGB from
(select tablespace_name, round(sum(bytes)/1024/1024/1024,1) as free_space
from dba_free_space group by tablespace_name UNION
select tablespace_name, round((free_space)/1024/1024/1024,1) as free_space from                                         dba_temp_free_space) a,
(select tablespace_name, sum(bytes)/1024/1024/1024 as tbs_size
from dba_data_files group by tablespace_name UNION
select tablespace_name, sum(bytes)/1024/1024/1024 tbs_size