Get the total size of the latest full backups on the SQL server

you can update –and backup_start_date > GETDATE()-1 or WHERE Position = 1 sections to get customized results.

WITH LastBackUp AS
(
SELECT bs.database_name,
bs.backup_size,
bs.backup_start_date,
bmf.physical_device_name,
Position = ROW_NUMBER() OVER( PARTITION BY bs.database_name ORDER BY bs.backup_start_date DESC )
FROM msdb.dbo.backupmediafamily bmf
JOIN msdb.dbo.backupmediaset bms ON bmf.media_set_id = bms.media_set_id
JOIN msdb.dbo.backupset bs ON bms.media_set_id = bs.media_set_id
WHERE bs.[type] = ‘D’ –and backup_start_date > GETDATE()-1
AND bs.is_copy_only = 0
)
SELECT sum( CAST(backup_size / 1048576 /1024 AS DECIMAL(10, 2) )) AS [Total_BackupSizeGB] FROM LastBackUp
WHERE Position = 1