select a.tablespace_name name,
b.tablespace_name dummy,
sum(b.bytes)/count(distinct a.file_id||'.'||a.block_id ) bytes,
(sum(b.bytes)/count(distinct a.file_id||'.'||a.block_id ))/1024/1024 tmb,
sum(b.bytes)/count(distinct a.file_id||'.'||a.block_id ) - sum(a.bytes)/count(distinct b.file_id ) used,
(sum(b.bytes)/count(distinct a.file_id||'.'||a.block_id ) - sum(a.bytes)/count(distinct b.file_id))/1024/1024 umb,
sum(a.bytes)/count(distinct b.file_id) free,
(sum(a.bytes)/count(distinct b.file_id)) / 1024 / 1024 fmb,
100*((sum(b.bytes)/count(distinct a.file_id||'.'||a.block_id )) - (sum(a.bytes)/count(distinct b.file_id ) ))/(sum(b.bytes)/count(distinct a.file_id||'.'||a.block_id)) pct_used
from sys.dba_free_space a, sys.dba_data_files b
where a.tablespace_name = b.tablespace_name
group by a.tablespace_name, b.tablespace_name

Thanks to Srinivas R Chandaka