subDirSize.ps1

#Inspired from ERIC COBB's script
$ErrorActionPreference= 'silentlycontinue'

$disk = Get-PSDrive S
"Disk size : " + "{0:N2}" -f ($disk.Used / 1GB) + " GB" + "  --  Free space : " + "{0:N2}" -f ($disk.Free / 1GB) + " GB"


$startDirectory = 'S:\'

$directoryItems = Get-ChildItem $startDirectory | Where-Object {$_.PSIsContainer -eq $true} | Sort-Object

foreach ($i in $directoryItems)
{
    $subFolderItems = Get-ChildItem $i.FullName -recurse -force | Where-Object {$_.PSIsContainer -eq $false} | Measure-Object -property Length -sum | Select-Object Sum
    if ( $subFolderItems.sum / 1GB -gt 0.01)
    {
        $i.FullName + " -- " + "{0:N2}" -f ($subFolderItems.sum / 1GB) + " GB"
    }
    else
    {
        $i.FullName + " -- " + "{0:N2}" -f ($subFolderItems.sum / 1MB) + " MB"
    }
}