how much space does sql server take per row

SELECT 
    TableName = t.NAME,
    SchemaName = s.Name,
    [RowCount] = p.rows,
    TotalSpaceMB = CONVERT(DECIMAL(18,2), SUM(a.total_pages) * 8 / 1024.0), 
    UsedSpaceMB = CONVERT(DECIMAL(18,2), SUM(a.used_pages) * 8 / 1024.0),
    UnusedSpaceMB = CONVERT(DECIMAL(18,2), (SUM(a.total_pages) - SUM(a.used_pages)) * 8 / 1024.0)
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 
    TotalSpaceMB DESC