Estimating the Required Space

The size allocation decisions you make about devices and databases are important because it is difficult to reclaim storage space after it has been assigned.

You can always add space; however, you cannot deallocate space that has been assigned to a database, unless you drop the database.

You can estimate the size of the tables and indexes for your database by using sp_estspace or by calculating the value. See Performance and Tuning Series: Physical Database Tuning > Determining Sizes of Tables and Indexes.