Retrieve Disk Space Per Database

select
    sys.databases.name,
    (sum(size) * 8 / 1024) as TotalDiskSpace,
    convert(varchar, sum(size) * 8 / 1024) + ' MB' as TotalDiskSpaceLabel
from (sys.databases join sys.master_files on sys.databases.database_id = sys.master_files.database_id)
group by sys.databases.name
order by sys.databases.name