// Change to your folder you want the size of
var folder = "F:\\winnt";
// Create FSO and Grab the folder you defined
var fso = new ActiveXObject( "Scripting.FileSystemObject" );
var fl = fso.GetFolder( folder );
// Get the byte size of folder and sub folders. Format
// into MB as well.
var byteSize = fl.Size;
var mbSize = new String( byteSize / 1048576 ).substr( 0, 5 );
// Create display message
var msg = "The size of " + folder + " is\n";
msg += byteSize + " (bytes)\n";
msg += mbSize + " MB\n";
// Show it
WScript.Echo( msg );