How to find total size of database

select
( select sum(bytes)/(1024*1024*1024) data_size from dba_data_files ) +
( select nvl(sum(bytes),0)/(1024*1024*1024) temp_size from dba_temp_files ) +
( select sum(bytes)/(1024*1024*1024) redo_size from sys.v_$log ) +
( select sum(BLOCK_SIZE*FILE_SIZE_BLKS)/(1024*1024*1024) controlfile_size from v$controlfile) "Size in GB"
from
dual