sys.sysfiles report on size, but that's just the current size of the file. Is there a way to find out what the initial size of the tempdb datafiles will be after it's recreated during a system restart?
A restart of SQL Server will reset the size of tempdb to its last configured size which is the last explicit size that was set by using a file sizing operation like ALTER DATABASE that uses the MODIFY FILE Option or DBCC SHRINKFILE command.
If you have not changed the tempdb size through any of the above commands, then it gets reset to MODEL database size.
Get current size of tempdb :
SELECT SUM(size)*1.0/128 AS [Tempdb size in MB] FROM tempdb.sys.database_files
Below will explain the value of proper sizing of tempdb :