There is no दिया length या to the number of pages a chapter should be. I've seen chapers with as little as 3 words ... and I'm pretty sure I saw a chapter with only 1 but that might have been in a kiddy book so that might not count. But anyway, I've also seen chapters like 14 pages plus! And personally, my chapters are like novels in themselves! Ask anyone whos read them! So, basically, go on for as long as आप want या need to go! GO WITH THE KEYPAD!
I've seen chapters that are a single page, and then I've seen chapters that are twenty pages! Heck, I once saw one that was forty pages (though that was a REALLY long chapter...) so it's whatever the necessary length needs to be. Just make sure it's not overly-wordy, nor should it be deprived of detail ^_^