If a chapter is a single sentence, it’s one sentence. If it’s twenty thousand words, it’s twenty thousand words. Chapters can be as long or short as you think it’s necessary—if a scene, a few scenes, or an overall theme is contained within that chapter. There is no sweet spot for every story in the world.
Genre can dictate the length of chapters. Horror tends to have short chapters because it keeps up the tense atmosphere, similarly to intense action scenes using short sentences. Romance has longer chapters because description and feelings are beginning to take priority, so scenes can be lengthier. Fantasy that introduces an entire world or culture tends to have even longer chapters than romance because this information is pertinent. But, just because this is a trend among these genres, it doesn’t mean you have to follow it. You can have long chapters in horror just as much as you can have short chapters in fantasy if you feel it works for your story.
Media and where you post can dictate how long your chapters are. For sites that aren’t mobile friendly, most readers read from a computer, so longer chapters are welcomed, but, for sites such as Wattpad where 80% of the readers read from their smartphones, shorter chapters are recommended if you care about numbers and stats . You can still post epically long chapters and still get dedicated readers, they’ll just more than likely be reading from the computer. I think if the mobile version would load longer chapters properly, there would be more people willing to read stories with longer chapters.
Even if you’re still worried about readers being bogged down by lengthy chapters, you can break up chapters to give readers a reprieve while still being easy to find their place later. Time skips, location skips, POV switches, and other things have been published before. The only reason for “boring” chapters is because seemingly nothing happens in it. Breaking up the chapter won’t fix that, you’ll just have numerous boring chapters in a row.
Keeping a consistent word count can help with being on schedule for your readers, but sometimes this sacrifices pacing and cutting scenes in the middle or forcing chapters to be longer than necessary. It’s entirely up to you.
I used to write 2000 word chapters, but, looking back on it, I see that I could have combined chapters, cut chapters, and just changed everything. I don’t like what I have done. Preferably, I write longer chapters, but it depends on the demands of the story. I also prefer to read long chapters. In fact, if chapters of online stories are consistently shorter than a thousand words, I don’t even bother.