The below procedure will return the size occupied by the indexes in a table. This will be helpful to measure the size before and after the maintenance activities.

Create Proc SQLZealot_FindIndexSize( @OBJECT_NAME  VARCHAR(255) )
 As
 Begin
 DECLARE @temp         TABLE
   (
    indexID BIGINT,
    objectId BIGINT,
    index_name NVARCHAR(MAX),
    used_page_count BIGINT,
    pages BIGINT
   )
 --Insert into temp table
 INSERT INTO @temp
 SELECT P.index_id,
     P.OBJECT_ID,
     I.name,
     SUM(used_page_count),
     SUM(
      CASE 
     WHEN (p.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
     )
 FROM   sys.dm_db_partition_stats P
     INNER JOIN sys.indexes I
    ON  I.index_id = P.index_id
    AND I.OBJECT_ID = P.OBJECT_ID
 WHERE  p.OBJECT_ID = OBJECT_ID(@OBJECT_NAME)
 GROUP BY
     P.index_id,
     I.Name,
     P.OBJECT_ID;
 SELECT index_name INDEX_NAME,
     LTRIM(
      STR(
       (
        CASE 
       WHEN used_page_count > pages THEN (used_page_count - pages)
       ELSE 0
        END
       ) * 8,
       15,
       0
      ) + ' KB'
     ) INDEX_SIZE
 FROM   @temp T
End

/*-----Usage:*/
exec SQLZealot_FindIndexSize 'mas_user'