Two methods show here on how to increase or decrease the tempdb size of MSSQL Server. Below exercise was done in MSSQL Server 2008 R2.
MSSQL Server Management Studio
You can use MSSQL Server Management Studio to increase or decrease the tempdb. In MSSQL Server Management Studio, expand the Databases and right click on tempdb. Choose Properties. Go to Files page. On this page, you can increase or decrease the tempdb size.
Transact-SQL
Use below command to increase or decrease the tempdb
ALTER DATABASE tempdb MODIFY FILE (NAME = 'tempdev', SIZE = NEW_SIZE_MB)
ALTER DATABASE tempdb MODIFY FILE (NAME = 'templog', SIZE = NEW_SIZE_MB)
