Depends a lot on your handwriting. Generally though, it comes out to a 4:3 ratio, with for every 4 lines written, there are only 3 lines typed (12 point, legible font such as times new roman, 1 inch margins. MLA for you fancy people). But like I said, it varies from person to person.
That would depend on writing size and the size/type of font you use. I find that (with me at least) one sheet handwritten is about one and 3/4 sheets typed with size 11 Times New Roman.
Font size? Yeah, there are a lot of variables to take in, like the size of your writing and the neatness and stuff like that.
It would all depend on the font size. Usually, the default font size in Word is 12. But, say your handwriting in bigger or smaller than that. If you write a story of paper, it may be longer than four pages in Word or it may be shorter. It all depends on what font size it is.