It depends a lot on the size of the page, the size of the print. To get a rough estimate, you can count the number of lines and number of words per line. A full length novel is generally 50,000 words or more, though you might be able to get away with shorter lengths for young adult or middle grade fiction.
If you're interested in seeing a lot of info on words per page, there are a lot of threads that already deal with the subject. If you enter words per page in the Google custom search at the bottom left of the page, you should find a lot of info for your enjoyment. Just adding this because a lot of new members don't know about the Google custom search. It's much better than the search at the top of the page.