Manuscript Word Counts
Word count is one of the most confusing things out there when it comes to writing. Everyone knows you need to pay attention to word count, but no one can really tell you what word count you should be going for.
There are some agents, like Kristin Nelson, who say you shouldn’t pay attention to word count, because if your story is compelling and saleable, it doesn't matter how long it is. But many other agents do care about word count, and for good reason - publishers pay attention to word count because longer books are more expensive to publish, and books shorter than the genre norm may not look appealing to readers on a shelf. If you fall wildly outside of the accepted ranges, you risk being auto rejected by agents.
KidLit
For children’s books, here are the generally accepted guidelines, sourced from here, here, and here:
Picture Books: 0-1,300 words
Early Reader: 100-2,500
Chapter Book: 4,000-13,000
Lower MG: 30,000-40,000
Upper MG: 30,000-60,000
MG SFF: 35,000-75,000
YA Contemporary: 60,000-75,000
YA SFF / Speculative: 85,000-95,000
Note that these are broken down by age range and genre. Usually, science fiction and fantasy are allowed longer word counts, to fit genre expectations surrounding world building.
Adult
For adult books, the generally accepted range is 80,000-100,000 words. Writer’s Digest breaks it down according to the following:
Below 70,000: Too short
70,000 - 79,999: Might be too short; probably all right
80,000 - 89,999: Totally cool
90,000 - 99,999: Generally safe
100,000 - 109,999: Might be too long; probably all right
110,000 or above Too long
What To Do If Your Word Count Differs
There’s a difference between being slightly off of the recommended word count for your age range and genre (i.e. having a 106,000 word adult novel, having a 99,000 YA fantasy) and being very off (i.e. having a 230,000 word middle grade).
If you’re very off, you need to edit. If you’re under the word count (i.e. a 60,000 word YA fantasy), consult with alpha and beta readers to see how you can make the book more complex, including how you can make character development more thorough and how you can amp up the plot. In this case, consulting a resource like Jessica Brody’s Save the Cat Writes a Novel can help you get a sense of what “beats” your story should be hitting, including what side plots should be incorporated into your manuscript to add length.
If you’re over the word count, you need to decide what to cut. If you’re wildly over the word count, this might be easy - split it into two or more books! If you’re just 10,000-50,000 words over (or so), you’ll need to decide what to cut. This might be language (like filler/filter words) or it might be extraneous side quests that don’t lend anything to the main plot. Ask your readers if there were places you lost their attention, which is usually a good sign that editing can be done.