create table #t

(name varchar(255), rows bigint, reserved varchar(20), data varchar(20), index_size varchar(20), unused varchar(20)) 

exec sp_MSforeachtable "insert into #t exec sp_spaceused '?'"  

select SUBSTRING(t.reserved, 0, CHARINDEX('KB', t.reserved)-1), *

from #t t

order by cast(SUBSTRING(t.reserved, 0, CHARINDEX('KB', t.reserved)-1) as int) desc

drop table #t