How long should a novel really be? The answer depends on the genre. Today I will share with you commonly accepted word found per genre but bear in mind that this is not an exact science. This is simply a guide for you to have in mind. If your story requires more words due to world-building or character development, by all means, go for it. If, on the other hand, your particular story doesn't need as many words as expected for your genre, do not dilute the writing just for the sake of reaching the ideal word count. Strive for these numbers, but not at all costs.

Now, before we get to genres, let me quickly define the length. Again, different people will define these numbers very differently. This is what I find to be the consensus.

Flash fiction 

300 - 1,000 words 

Short fiction

1,000 - 7,500 words

Novelette

7,500 - 17,000 words

Novella

17,000 - 40,000 words

Novel

40,000+ words based on a genre

Ok, so now that we know how to define the length in general, let's see what the expectations are based on the major genres, assuming you're writing a novel. 

Adult fiction

80,000 - 100,000 words

Young adult

55,000 - 100,000 words (ideally between 60,000 and 90,000)

Romance

50,000 - 100,000 words (ideally around 70,000)

Science fiction

50,000 - 150,000 words (ideally between 90,000 and 120,000)

Fantasy

50,000 - 150,000 words (ideally between 90,000 and 120,000)

Crime

40,000 - 90,000 words (ideally between 70,000 and 80,000)

Mystery

Horror

Contemporary

60,000 - 90,000 words

Historical

80,000 - 10,000 words

Dystopian

60,000 - 120,000 words

Now let's move on to non-fiction.

Non-fiction

70,000 - 80,000 words

How-to and self-help

30,000 - 70,000 words (ideally between 40,000 and 50,000)

Memoir

45,000 - 100,000 words (ideally around 80,000 words)

Biography

80,000 - 20,000 words

And there you have it. Use these numbers as a guide, but remember that when it comes to this topic, different people will give you different answers. Based on my research and comparison, I was able to find the middle ground that covers most of the different opinions on this matter, yet still narrow it down using ideal numbers for each genre.