Oracle Database Discussions

Hi,

I want to know size of my database. I have used below query, it is showing 83GB.

SELECT sum((df.bytes/(1024*1024*1024)) )t

   FROM dba_data_files df;

But when i checked in home directory as below, it is showing different size

[oracle@mydb ~]$ df -H .

Filesystem             Size   Used  Avail Use% Mounted on

/dev/mapper/VG_home-LV_home

                        43G    21G    20G  52% /home

Kindly clarify why both are showing different values and which value i need to consider for size my database.