How to know DB size using backup file without restoring it

Is there anyway so that we can estimated/know size of database using backup file without restoring it?

Yes, there is, though you got to use RESTORE command anyway. Instead of RESTORE DATABASE, use RESTORE FILELISTONLY to get a detailed view of files in the backup. The Size column tells the file size in bytes.

RESTORE FILELISTONLY FROM DISK = N'v:\MyBackup.bak'

StackExchange Database Administrators Q#62527, answer score: 12