According to Writer's Digest Magazine, here are the average word counts by genre. Keep in mind that each publishing company, agent, and editor will have their own specific expectations for word counts. These are benchmarks to be aware of - but not necessarily rules written in stone.
Non-Fiction: average 50,000, depending on topic
Fiction: Short story: any fictional work under 7,500 words Novelette: between 7,500 and 17,500 words Novella: between 17,500 and 40,000 words Novel: anything over 40,000
Adult & New Adult Novels: Commercial & Literary:
80,000 – 89,999: Totally cool
90,000 – 99,999: Generally safe
70,000 – 79,999: Might be too short; probably all right
100,000 – 109,999: Might be too long; probably all right