I had the same problem and found a different answer. I found that getting the height of a div that's height is determined by its contents needs to be initiated on window.load, or window.scroll not document.ready otherwise i get odd heights/smaller heights, i.e before the images have loaded. I also used outerHeight().
var currentHeight = 0;
$(window).load(function() {
//get the natural page height -set it in variable above.
currentHeight = $('#js_content_container').outerHeight();
console.log("set current height on load = " + currentHeight)
console.log("content height function (should be 374) = " + contentHeight());
});