Design a database, you may have to estimate how large the database will be when filled with data. Estimating the size of the database can help you determine the hardware configuration you will require to do the following:
Achieve the performance required by your applications.
Guarantee the appropriate physical amount of disk space required to store the data and indexes.
https://docs.microsoft.com/en-us/sql/relational-databases/databases/estimate-the-size-of-a-database?view=sql-server-ver15