When do you know how many chapters are going to be in your novel?
Some people outline each chapter before they start writing. Some people don't know how many chapters they'll have until they type "The End." I'm somewhere in between. Usually after I pass the halfway point of the first draft, I can map out how many more scenes I need and guess how long each scene will be. It's not 100% foolproof, and I've certainly had to go back while revising to insert "Chapter 3A". But after I'm half done with the first draft, I can make an educated guess as to chapter count (and a less educated, but somewhat accurate word count).
So today it's time for a poll. When do you estimate how many chapters will be in your book?
-- Kate, Miss Perfecting the Pages