HTML document + js + images size in kb

I want to be able to find out how long a page will take to download. I can calculate how long it will 开发者_JAVA技巧take when I know the size of the page including html page, javascript and images (including background images).

Is there a way to calculate this easily? Or an online resource perhaps?

Currently I use FF's Web Developer toolbar that shows the document size, but not with background images...

try Firebug. Theres a tab named "network". All loaded files are shown there with size.