Answer: As long as you think it needs to be.
Can it only be told in 2000 words or is 200,000 a better fit?
It shouldn’t matter how long or short a story is, what matters is its content. If your story can be best told in a short story, then don’t ruin it by making it longer. On the other hand if your story can be best explained only if it is over 100,000 words then don’t shorten it.
Your story is a work of art, whether you realized it or not. If your feedback from other people is that they felt it was too long or too short then they are probably picking up on something (thought keep in mind that not all people are smart and not everyone’s opinion should be taken into account).
Maybe your story can only be told in 6 words?
Or only as flash fiction, a story that is up to 2000 words?
What about micro-fiction? Under 300 words sound good? 55 fiction is a good example.
Since we’re talking about such short stories, what about a Drabble? Yes it is a real thing – only 100 words. Designed to test an author’s ability to express something in a short constraint.
Now we are getting into the short story section. Depending on who you talk to these can go up to 7,500 to 9,000 or even 20,000 by today’s standards.
If you go any bigger you enter the Novelette and Novella categories. These are usually long short stories that does not quite make it to a regular novel length. A novelette can range from 7,500 to 20,000 words. Novellas can be 17,500 to 40,000, or 20,000 to 50,000 words.
Getting confused yet? Yes, then your not alone. I only just found out about novelettes.
Novels can be anywhere from 50,000 to 110,000 words by one estimate, or even just a general 40,000+ range. Word count varies depending on genres.
Anything over 110,000 should be considered epics.
In the end a story is along as you want it to be. And that can be anywhere from one words to one million.