SQL Server Database Size Ordered by Size

Get the database sizes for all databases on a SQL Server Instance

 SELECT
database_name = DB_NAME(database_id)
, log_size_mb = CAST(SUM(CASE WHEN type_desc = 'LOG' THEN size END) * 8. / 1024 AS DECIMAL(8,2))
, row_size_mb = CAST(SUM(CASE WHEN type_desc = 'ROWS' THEN size END) * 8. / 1024 AS DECIMAL(8,2))
, total_size_mb = CAST(SUM(size) * 8. / 1024 AS DECIMAL(8,2))
FROM sys.master_files WITH(NOWAIT)
--WHERE database_id = DB_ID() -- for current db
GROUP BY database_id
order by CAST(SUM(size) * 8. / 1024 AS DECIMAL(8,2)) desc

REF: http://stackoverflow.com/a/18014581