Chapters may be very short, or very long, but they're usually about enough for a person to read one or two chapters before going to sleep at night. I'd say, somewhere between 1,000 and 6,000 words. Much shorter than 1000 and it feels a bit flimsy; over 6,000 and it starts to feel a bit unwieldy. (This is a generalisation and you'll be able to point to lots of writers who write longer chapters - JK Rowling comes to mind.)
I always recommend writing in scenes rather than chapters, and if you think scenes being between 500-3,500 words, then you're going to have anything from 1 to 5 scenes in a chapter. If you're the sort of person who likes to do a lot of forward planning (and I'm not) you might work on a scheme of 3 scenes per chapter, each scene 1,000 to 2,000 words long. Twenty chapters like this, averaging 4,000-5,000 words and you've got a complete novel. It's not my way of working, but it could work for you.
Vary the length of your chapters so the reader is constantly surprised and so drawn into continuing to read. Shorter chapters increase the pace, so it's usually good for them to get shorter towards the end of the novel (again, that's a generalisation). Finally, however long you make them, give your chapters good must-carry-on-reading endings.