I'm finding all of this very helpful! I just wrote a prologue that ended up right at 500 words, and I wanted to know the same. Another interesting way to find a good chapter length I think, would be to sit down and read a book from the first chapter, for about 5-10 minutes, or however long you wish your chapters to be, and see how many words you have read in that amount of time.
I go by chapter gauge when I read, and when I was young I would discipline my reading habits, by posing a limit to the quantity of chapters I could read before allowing bed, or other distractions to overtake me.
Say for instance you are writing a YA novel, and want the chapters to be gripping, but not too lengthy.
You could either borrow a young adult to test it out, and tell you when their mind starts to float, or put yourself in the mindset of a young adult with school, work, friends, etc on their mind, and see how long you can pay attention to one situation with other things surrounding you.
I like to read for about 30 minutes, and then continue working, and it's slightly perturbing to spend a half hour in attempt to discover something that could have easily been resolved in 10 minutes, and be stuck in the same spot you started in. Like a "to be continued" in TV shows, one is suspenseful, two in a row is annoying, three is aggravating.
These are just my personal thoughts, as a busy individual with not as much time to devote to reading as I'd like.