Display current page width in px and ems - jQuery

$(document).ready(function() {
    $("<div id='screenwidth' style='position:fixed;right:0;bottom:0;background-color:#339;color:#fff;padding:3px;font-size:9px;'></div>").appendTo("body");

    function getWindowSize(){
        var windowWidth = $(window).width();
        var windowWidthEms = windowWidth / 16;
        $("#screenwidth").text(windowWidth+"px, "+Math.round(windowWidthEms)+"em");
    }

    getWindowSize();

    $(window).resize(function() {
        getWindowSize();
    });
});