get Website Site ID (SID) on sharepoint with powershell

example code :

Add-PSSnapin Microsoft.SharePoint.Powershell -ErrorAction SilentlyContinue
$webURL = "http://SERVER:PORT/sites/TEST/"
$web = Get-SPWeb -Identity $webURL
$web.ID

Capture

source : http://anthony-verschraegen.blogspot.com/2013/04/sharepoint-powershell-get-web-id-guid.html