I'm going to paste in some very useful stuff, so you can't use not knowing as an excuse not to write :) First word count, then there's stuff about chapters in the next bit. I wouldn't get too wedded to the AMOUNT of chapters and word count in each, but I would say that the rough template of what should happen in each that's below is pretty helpful.
WORD LENGTHS FOR KIDS BOOKS
If age 5-6 = c 5,000 words; if 6-8 = 7-10,000; if 7-9 c 12-15,000, and 9-11 are c 20-30,000.
Chapter books are for more independent readers who are making the bridge between picture books and early readers and middle grade. Some bookstores designate these as for kids 9-12 but I would say readers are mostly 6-8. Manuscripts can range from about 5,000 words to about 15,000 words, max. Since your audience is still developing its reading skills, you have more of a wide berth in terms of vocabulary and sentence structure, story and character. Younger chapter books will be simpler, but you can get pretty sophisticated for older chapter books. Trim size resembles paperback books and finished books tend to go from 100 to 160 pages, with black and white spot illustrations throughout. Some of my favorite chapter books are CLEMENTINE by Sarah Pennypacker and illustrated by Marla Frazee, the IVY AND BEAN series, written by Anne Barrows and illustrated by Sophie Blackall from Chronicle Books, and the fun GERONIMO STILTON and THEA STILTON books from Scholastic (in full color!). If you’re at all curious about chapter books, do pick some up and take a look. They’re a very quick read!
. But while I was toying with the idea of a chapter book, I thought about how to convey a whole novel in approximately 4,000 words. There must be a formula for children’s books I mused to myself. How else can you quickly and easily keep yourself on track with the story arc and things like establishing characters, setting up conflict, bringing in action, building to the climax, resolution, etc.
Being a bit of a research nerd (or just plain old nerd if you prefer) I turned to a few chapter books and created a formula. So, if you are thinking of writing a short chapter book, this formula might help you out.
Here’s what I found:
Chapter 1: Introduction to backstory, setting and main characters established along with their goal.
Chapter 2: Introduction of story problem
Chapter 3-4: Conflict introduced and builds
Chapter 5: Final build up of conflict leading to story’s climax
Chapter 6: Resolution
To come up with this formula, I took three chapter books from the Rainbow Magic series by Daisy Meadows and ran them through the formula wringer (me). In this case, the book reading levels ranged from 4.3 to 4.9. The books are aimed at ages 6-9. Word counts vary from 4059-4254. Pages range from 65-67. 6 Chapters per book. Chapters tend to be about 8-10 pages long.
There you go. Zero to sixty and back to zero again in sixty pages. How sweet it is. I suppose I could also apply this to middle grade novels, but stretch it out a bit more, taking more time to establish details and deepen the conflict.