If you need to know the size of all your tables, here’s a simple query to get you where you need to go:
SELECT t.NAME AS TableName, s.Name AS SchemaName, p.rows AS RowCounts, SUM(a.total_pages) * 8 AS TotalSpaceKB, SUM(a.used_pages) * 8 AS UsedSpaceKB, (SUM(a.total_pages) - SUM(a.used_pages)) * 8 AS UnusedSpaceKB FROM sys.tables t INNER JOIN sys.indexes i ON (t.OBJECT_ID = i.object_id) INNER JOIN sys.partitions p ON (i.object_id = p.OBJECT_ID AND i.index_id = p.index_id) INNER JOIN sys.allocation_units a ON (p.partition_id = a.container_id) LEFT OUTER JOIN sys.schemas s ON (t.schema_id = s.schema_id) WHERE t.NAME NOT LIKE 'dt%' AND t.is_ms_shipped = 0 AND i.OBJECT_ID > 255 GROUP BY t.Name, s.Name, p.Rows ORDER BY UsedSpaceKB desc