Подключаешься к серверу БД с помощью SQL Server Management Studio (SSMS) и выполняешь SQL запрос:
SELECT t.NAME AS TableName,
s.Name AS SchemaName,
p.rows,
SUM(a.total_pages) * 8 AS TotalSpaceKB,
CAST(ROUND(((SUM(a.total_pages) * 8) / 1024.00), 2) AS NUMERIC(36, 2)) AS TotalSpaceMB,
SUM(a.used_pages) * 8 AS UsedSpaceKB,
CAST(ROUND(((SUM(a.used_pages) * 8) / 1024.00), 2) AS NUMERIC(36, 2)) AS UsedSpaceMB,
(SUM(a.total_pages) - SUM(a.used_pages)) * 8 AS UnusedSpaceKB,
CAST(ROUND(((SUM(a.total_pages) - SUM(a.used_pages)) * 8) / 1024.00, 2) AS NUMERIC(36, 2)) AS UnusedSpaceMB
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 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,
t.Name