Temporary Tables and Their Size

SELECT TBL.name AS ObjName

      ,STAT.row_count AS StatRowCount

      ,STAT.used_page_count * 8 AS UsedSizeKB

      ,STAT.reserved_page_count * 8 AS RevervedSizeKB

FROM tempdb.sys.partitions AS PART

      INNER JOIN tempdb.sys.dm_db_partition_stats AS STAT

      ON PART.partition_id = STAT.partition_id

      AND PART.partition_number = STAT.partition_number

      INNER JOIN tempdb.sys.tables AS TBL

      ON STAT.object_id = TBL.object_id

ORDER BY TBL.name;