Mailbox Folder Size

Get-MailboxFolderStatistics username | select name, folderpath,
    @{Name="foldersize"; Expression= {$_.foldersize.tokb()}},
    @{Name="FolderAndSubfolderSize"; Expression= {$_.FolderAndSubfolderSize.tokb()}} |
    Export-Csv -NoTypeInformation C:\Temp\user_foldersize.csv

Get-MailboxFolderStatistics username | select name, folderpath, foldersize, FolderAndSubfolderSize | Export-Csv -NoTypeInformation C:\Temp\user_foldersize.csv