How long is a middle-grade or young adult novel?
As long as it needs to be — mostly. Granted, it might be a bit tougher to sell a story that is especially long or short, but it is even tougher, if not impossible, to sell a book that has been padded or chopped for the sake of hitting a preselected length. A book can be shorter than Sarah, Plain and Tall, or longer than Hitty, Her First Hundred Years. The typical range is 35-65 pages for a chapter book, 45-90 for a low-middle-grade, 90-120 for a middle-grade, 150-200 for a young, young adult, but these are just averages. Some publishers have series of books with a maximum of pages. For example, Hyperion chapter book manuscripts must currently be 2,500-5,000 words maximum. If you have questions about specific series of books, do some research — read the books, check the catalogue, contact the publisher, etc.