1. Microsoft SQL Server Managementstudio öffnen

2. Zur Datenbank wechseln und per rechte Maustaste ein Abfragfenster öffnen.

3. Folgende SQL-Anweisung ausführen 

with cte as (  
  SELECT  
  t.name as TableName,  
  SUM (s.used_page_count) as used_pages_count,  
  SUM (CASE  
              WHEN (i.index_id < 2) THEN (in_row_data_page_count + lob_used_page_count + row_overflow_used_page_count)  
              ELSE lob_used_page_count + row_overflow_used_page_count  
          END) as pages  
  FROM sys.dm_db_partition_stats  AS s   
  JOIN sys.tables AS t ON s.object_id = t.object_id  
  JOIN sys.indexes AS i ON i.[object_id] = t.[object_id] AND s.index_id = i.index_id  
  GROUP BY t.name  
  )  
  ,cte2 as(select  
      cte.TableName,   
      (cte.pages * 8.) as TableSizeInKB,   
      ((CASE WHEN cte.used_pages_count > cte.pages   
                  THEN cte.used_pages_count - cte.pages  
                  ELSE 0   
            END) * 8.) as IndexSizeInKB  
  from cte  
 )  
 select TableName,TableSizeInKB,IndexSizeInKB,  
 case when (TableSizeInKB+IndexSizeInKB)>1024*1024   
 then cast((TableSizeInKB+IndexSizeInKB)/1024*1024 as varchar)+'GB'  
 when (TableSizeInKB+IndexSizeInKB)>1024   
 then cast((TableSizeInKB+IndexSizeInKB)/1024 as varchar)+'MB'  
 else cast((TableSizeInKB+IndexSizeInKB) as varchar)+'KB' end [TableSizeIn+IndexSizeIn]  
 from cte2  
 order by 2 desc