A quick google brought me the below SQL and I been using this sql a lot.
SELECT OBJECT_NAME (sc.[id]) tablename
, COUNT (1) nr_columns
, SUM (sc.length) maxrowlength
FROM syscolumns sc
join sysobjects so
on sc.[id] = so.[id]
WHERE so.xtype = 'U'
GROUP BY OBJECT_NAME (sc.[id])
ORDER BY SUM (sc.length) desc
