filled datafiles

I want to see how much datafiles are filled.
We have 20 datafiles in DB, size of DB is 35GB.
but I want to know how much of this files is used.

Paresh

The following query will list you total occupied space in each file. From the size of each file you can conclude how much free space is left in each of them.

select f.file_name, sum(e.bytes)
from dba_extents e, dba_data_files f
where e.file_id = f.file_id
group by file_name;

Or you can go with DBA_FREE_SPACE to list the available space in each datafile:

select f.file_name, sum(fs.bytes)
from dba_free_space fs, dba_data_files f
where fs.file_id = f.file_id
group by file_name;