SharePoint Online: Get Document Library Size using PowerShell

#Load SharePoint CSOM Assemblies
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.dll"
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.Runtime.dll"
   
#Function to Get the size of a List or Library in SharePoint Online
Function Get-SPOListSize($SiteURL, $ListName)
{ 
     Try
     {
        #Get credentials to connect to SharePoint Online
        $Cred = Get-Credential
 
        #Set up the context
        $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
        $Ctx.Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.Username, $Cred.Password)
     
        #get the list
        $List = $Ctx.Web.Lists.GetByTitle($ListName)
        $Ctx.Load($List)
        $Ctx.ExecuteQuery()

        #Query to Get all List Items from all folders - exclude Folder objects
        $Query = New-Object Microsoft.SharePoint.Client.CamlQuery
        $Query.ViewXml = "<View Scope='RecursiveAll'><Query><OrderBy><FieldRef Name='ID' Ascending='TRUE'/></OrderBy></Query><RowLimit Paged='TRUE'>2000</RowLimit></View>" 
        $i=1;$TotalSize = 0
        Do {
            #Get items from the list in batches
            $ListItems = $List.GetItems($Query)
            $Ctx.Load($ListItems)
            $Ctx.ExecuteQuery()
            $Query.ListItemCollectionPosition = $ListItems.ListItemCollectionPosition

            ForEach($ListItem in ($ListItems| Where {$_.FileSystemObjectType -eq "File"}))
            {
                #Get the File
                $File = $ListItem.File
                $Ctx.Load($File)
                $Ctx.Load($File.Versions)
                $Ctx.ExecuteQuery()
                Write-host -f Yellow "Size of '$($File.Name)' Item ($i of $($List.ItemCount)) - " -NoNewline
 
                $FileSize =0; $VersionSize = 0
                If($File.Versions.Count -ge 1)
                {
                    $VersionSize = $File.Versions | Measure-Object -Property Size -Sum | Select-Object -expand Sum
                }
                $FileSize =  $ListItem.File.Length  + $VersionSize
                Write-host "$($ListItem.File.Length) + $VersionSize :" $FileSize
                $TotalSize += $FileSize
                $i++
                #Clear
            }
        } While ($Query.ListItemCollectionPosition -ne $null)
        Return [Math]::Round($TotalSize/1MB, 2)
    }
    Catch [System.Exception]
    {
        Write-Host -f Red "Error:"$_.Exception.Message
    }
}
   
#parameters
$SiteURL = "https://crescent.sharepoint.com/sites/marketing"
$ListName="Branding"

#Call the function to get document library size
$LibrarySize = Get-SPOListSize -SiteURL $SiteURL -ListName $ListName
Write-host -f Green "`nToal Size of the list/library: $LibrarySize MB"

#Set Variables
$SiteURL = "https://crescent.sharepoint.com/sites/Marketing"
$LibraryName = "Documents"
 
#Connect to SharePoint Online site
Connect-PnPOnline -Url $SiteURL -Interactive

$FileData = @()
#Iterate through all files
Get-PnPListItem -List $LibraryName -PageSize 500 | Where {$_.FieldValues.FileLeafRef -like "*.*"} | ForEach-Object {
    Write-host "Getting Size of the File:"$_.FieldValues.FileRef -NoNewline
    #Get FileSize & version Size
    $FileSizeinKB = [Math]::Round(($_.FieldValues.File_x0020_Size/1KB),2)
    $File = Get-PnPProperty -ClientObject $_ -Property File
    $Versions = Get-PnPProperty -ClientObject $File -Property Versions
    $VersionSize = $Versions | Measure-Object -Property Size -Sum | Select-Object -expand Sum
    $VersionSizeinKB = [Math]::Round(($VersionSize/1KB),2)
    $TotalFileSizeKB = [Math]::Round(($FileSizeinKB + $VersionSizeinKB),2)
    Write-host `t $TotalFileSizeKB "KB" -f Yellow

    #extract File Size data
    $FileData+=New-Object PSObject -Property  ([Ordered]@{
        "File Name"  = $_.FieldValues.FileLeafRef
        "File URL" = $_.FieldValues.FileRef
        "File Size (KB)"  = $FileSizeinKB
        "Version Size (KB)"   = $VersionSizeinKB
        "Total File Size (KB)" = $TotalFileSizeKB
    })
}
$FileData | Format-table 
#Calculate the Total Size of the document library
$LibrarySize = [Math]::Round((($FileData | Measure-Object -Property "Total File Size (KB)" -Sum | Select-Object -expand Sum)/1KB),2)
Write-host -f Green "Total Library Size (MB):" $LibrarySize