Get Size of all individual databases and Total value – SQL server

SELECT d.NAME
,ROUND(SUM(CAST(mf.size AS bigint)) * 8 / 1024, 0) Size_MBs
,(SUM(CAST(mf.size AS bigint)) * 8 / 1024) / 1024 AS Size_GBs into #Totaldbsize
FROM sys.master_files mf
INNER JOIN sys.databases d ON d.database_id = mf.database_id
WHERE d.database_id > 4 — Skip system databases
GROUP BY d.NAME
ORDER BY d.NAME

select * from #Totaldbsize

SELECT sum (size_gbs) as TotalDBSize
FROM #Totaldbsize