$(window).height() vs $(document).height

I am having problem of getting wrong height with

$(window).height();

and got the similar question here

In my case when I try

$(document).height();

it seems to return me correct result

window height returns 320

while document height returns 3552!

I found this question too

But in my case window already gets loaded completely as I am calling height function after few ajax operations

So what is the best way to know the height of the current window?

Edit: