Oracle Database Discussions

hello,
I am using below query to calculate my database size

select (a.data_size+b.temp_size+c.redo_size+d.controlfile_size)/1024 "total_size in GB"
from ( select sum(bytes)/1024/1024 data_size
from dba_data_files a,
( select nvl(sum(bytes),0)/1024/1024 temp_size
from dba_temp_files ) b,
( select sum(bytes)/1024/1024 redo_size
from sys.v_$log ) c,
( select sum(BLOCK_SIZE*FILE_SIZE_BLKS)/1024/1024 controlfile_size
from v$controlfile) d;


now I just turn the archive log on, now I want to include archive log files size occupied.
How can I calculate size consumed by archive log files?I know that archive log files must move to backup media,but I want to estimate for x records.

regards,
tanveer