O Powershell possibilita da seguinte maneira:
Tamanho em MB
"Folder use {0:0,0.00} MB" -f (((Get-ChildItem -R C:\TEMP | measure-object length -Sum ).Sum / 1MB)
Tamanho em GB
"Folder use {0:0,0.00} MB" -f (((Get-ChildItem -R C:\TEMP | measure-object length -Sum ).Sum / 1GB)
Talvez em TB
"Folder use {0:0,0.00} MB" -f (((Get-ChildItem -R C:\TEMP | measure-object length -Sum ).Sum / 1TB)