Quality Essentials Suite

SELECT

    t.NAME AS TableName,

    s.Name AS SchemaName,

    p.rows AS RowCounts,

    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 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

    UsedSpaceMB desc

From https://stackoverflow.com/questions/7892334/get-size-of-all-tables-in-database