And it matters in more than one way, too.
People tend to make up their own definitions, but let me give you the industry-standard ones right up front…
Flash – Less than 1,000 words
Short Story – 1,001 to 7,499 words
Novelette – 7,500 to 17,499 words
Novella – 17,500 to 39,999 words
Novel – 40,000 to 79,999 words
Long Novel – 80,000 to 119,999 words
Jumbo Novel – More than 120,000 words
These are the lengths used throughout the publishing industry. Some publishers may have others like Super Flash (less than 500 words) and Super Novel (more than 160,000 words) but the above are pretty well universal.
The size of what you write makes a huge difference in your sales and income.
At first glance, it would seem bigger is better…after all, in general, a Long Novel will command a higher price than a Short Story. This first glance is true in terms of the dollars per sale, but there is more to the equation.
If we are talking about a fairly typical author, the general rule is you will sell fewer longer works at a higher price than you will shorter works at a lower price.
This implies shorter books may very well make more money for you, but there is a point of diminishing returns. That is, at some point your books become so short and are priced so high (in terms of cents per word) that no one will buy them.
Just a few caveats here…first, there are some authors who are known for long books. Stephen King could write a 10,000,000 word novel and price it at $500 and it will sell about the same number of copies as any of his (slightly) shorter works. Second, there are some genres where longer books are very popular. Hard science fiction comes to mind. Many publishers in this and similar genres won’t accept manuscripts below a certain size. Thirdly, readers come to expect works of a certain length from an author. This means if you are known for writing (let’s say) Long Novels, don’t be too surprised if your new Novella flops like a fish on the beach. And fourth, for ebook-only releases, shorter books (Novella or smaller) often sell very well because many readers will view the book on a mobile device while they have a few minutes of spare time, like waiting at the doctor’s office.
For most of us in most genres in today’s world of simultaneous print and ebook releases, the magic number is in the range of the upper half of Novella to the lower half of Novel as defined above. For those who don’t want to page up, that’s about 30,000 to 60,000 words.
There is one final money issue to keep in mind, especially if you self-publish…Amazon (and others) are kicking around (internally) the idea of charging higher fees for both very long works (they take up more server space and bandwidth to transfer) AND very short works (they still need a certain amount of storage and administration). There is a chance ebook publishers may jump on this bandwagon as well by paying (or at least offering) lower royalties on similarly-sized ebooks.
But the real bottom line for most authors is going to come down to finding a story length that both sells well and that you are comfortable working with. If either of these things is missing, you’re going to either go broke or crazy.