Get size of all tables in database

Determining space used for each table in a SQL Server

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 t.Name