The way I plotted out my current manuscript it should end up around 55,000 words and be just under 30 chapters. I spend each writing session getting down at least a third of a final-chapter's worth of plot progression, and I have a step outline of all of the major events. Minor things I sort of leave till when I'm working on a particular chapter.
Ideally you'll want chapters, or at least line breaks of some sort every few thousand words, simply because the time requirements of reading need some sort of breaks. As much as the ideal situation would be a reader going through the entire manuscript in one sitting, that's a very rare opportunity. I use chapters as scene breaks, POV shifts, or for other changes in the narrative. For instance, I may end a chapter with someone pulling a knife on the protagonist, and the dramatic need of how exactly the protagonist will deal with the threat drives a reader to continue past that chapter break.
It also depends on the way you're distributing chapters. If they are released serially, you have to have each chapter be sort of self-contained, but not necessarily a particular length.
A story I edit that is being released serially is currently at ~111,000 words and 16 chapters, but within those chapters there are plenty of breaks in the narrative. For that story, chapters each show a single progression in the story, describe a key event or shift in a character, or the like. But it all depends on what impression you want to accomplish in the story.