SELECT percent_complete,*
FROM sys.dm_exec_requests
WHERE session_id = 63 -- Remember to change session_id = to the relevant spid

/*

This simple script shows what percentage of a transaction has completed
This works for the following types of transaction:

ALTER INDEX REORGANIZE
AUTO_SHRINK option with ALTER DATABASE
BACKUP DATABASE
DBCC CHECKDB
DBCC CHECKFILEGROUP
DBCC CHECKTABLE
DBCC INDEXDEFRAG
DBCC SHRINKDATABASE
DBCC SHRINKFILE
RECOVERY
RESTORE DATABASE,
ROLLBACK
TDE ENCRYPTION
Change the 63 in the where clause to match the spid for your transaction.
Hint exec sp_who2 and look at command. This is the spid you want.

*/