Converting the FileSystemObject's Size Property
Definition: Returns the file size of a file or the folder size of a folder.
You can use the Get-Item cmdlet with the Length property to retrieve the size of a file:
It’s not quite as straightforward to retrieve the size of a folder. To do that, you need to retrieve the length of all files in the folder and add them up.
Here’s how you get the file size of all the files in a folder, not including subfolders:
Get-ChildItem C:\Scripts | Measure-Object -property length -sum
If you’d like to include subfolders, use the -recurse parameter:
Get-ChildItem C:\Scripts -recurse | Measure-Object -property length -sum