Show data and disk use breakdown by table

In SSMS, right-click on the database and go to "Reports", "Standard Reports", "Disk Usage by Table". It will tell you the total size, the data size, the index size, and the unused size for each table (as well as the row count).

It's been answered on Stack Overflow:

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

The query linked to, and copied by, @Nelson is inaccurate: it ignores Indexed Views, Full Text Indexes, XML Indexes, etc.

If you want a query that will include everything without executing sp_spaceused via sp_MSForEachTable, then I have already posted two variations of it (one here on DBA.StackExchange and the other on StackOverflow) so I won't copy them here:

• Per each Table / Indexed View: sp_spaceused - How to measure the size in GB in all the tables in SQL

• Per each Index: space usage on sys.allocation_units and sp_spaceused