Calculate the database size

SELECT 'DB Size' "*****"
,round(sum(round(sum(nvl(fs.bytes/1024/1024,0)))) /
sum(round(sum(nvl(fs.bytes/1024/1024,0))) + round
(df.bytes/1024/1024 – sum(nvl(fs.bytes/1024/1024,0))))
* 100, 0) "%FREE"
,round(sum(round(df.bytes/1024/1024 –
sum(nvl(fs.bytes/1024/1024,0)))) / sum(round(sum
(nvl(fs.bytes/1024/1024,0))) + round(df.bytes/1024/
1024 – sum(nvl(fs.bytes/1024/1024,0)))) * 100, 0)
"%USED"
,sum(round(sum(nvl(fs.bytes/1024/1024,0)))) "FREE MB"
,sum(round(df.bytes/1024/1024
– sum(nvl(fs.bytes/1024/1024,0)))) "USED MB"
,sum(round(sum(nvl(fs.bytes/1024/1024,0))) + round
(df.bytes/1024/1024
– sum(nvl(fs.bytes/1024/1024,0)))) "Size"
FROM dba_free_space fs, dba_data_files df
WHERE fs.file_id(+) = df.file_id
GROUP BY df.tablespace_name, df.file_id, df.bytes,
df.autoextensible
ORDER BY df.file_id;