Minimum 512 MB for Express; 1 GB is recommended for basic use, while 4 GB+ is suggested for production-level performance.
When you visit the download page, you will see several file options. Choosing the right one depends on your needs: download sql server database engine 2014
Includes both the database engine and SQL Server Management Studio (SSMS) , which is the primary interface for managing your databases. Minimum 512 MB for Express; 1 GB is
Approximately 4.2 GB to 6 GB of available space depending on the features selected. Minimum 512 MB for Express