How long should your novel be to be published? There is no simple answer to the question. Most adult novels are at least 60,000 words. The average adult fiction novel runs from 75,000 to 100,000 words. Non-fiction novels can have both more or less words but most publishable novels for the adult market, again, should be at least 60,000 words. Young adult and children's market novels are considerably shorter. They run on average from 45,000 to 75,000 words. Some novels aimed for a youthful audience are as short as 30,000 words.
However, if you are self publishing, your novel can be as long as you want. The nice thing about self publishers is that the author has complete control over their manuscript. The downside to this is that they are less likely to make money off of their published work. For authors who are more interested in getting their work out into the world and less interested in profits, this is a good route for you. Most writers don't have enough time in their lives for that. Writing a novel takes both time and effort and for those of us with little free time, it can be an uphill battle, especially if you work full time, go to school, or have children.
For those who are interested in mass markets and large publishing houses the guidelines set above are best. If your novel is too short, there won't be as much profit for the publishing house to make off of the book which makes them less inclined to publish it. On the other hand, if the novel is too long, they won't want to publish it either as the cost of production will eat into their profits.
How long is too long? That is a good question. Most novels over 120,000 words are less likely to be considered by large publishing houses. While novels in the Harry Potter and Game of Thrones series are examples of bestsellers with large word counts, those novels are exceptions to the rule. In this day and age there is a sort of golden number of pages a novel should be. A novel that has anywhere between 250 to 425 pages are the market standard. As each page within the average modern American novel has roughly 250 words each, the average word count usually falls between the 60,000 and 100,000 standard. Again, if you are self publishing, you get to have some leeway in this.
Having an industry standard novel length can seem rather arbitrary, but there are some good reasons behind the set word count. And I am not jut talking about profits, although those are important too. If a novel is too short, more often than not there are plot holes and/or a lack of development in characterization, scene, and plot. However if a novel is loo long there is usually to much exposition and overwriting. Most authors, myself included, have a tendency to write either too much or not enough. Finding the happy medium is why the industry norm is out there. It is a formula that has been tested, works well for the readers, the publishing houses, and hopefully works well for the author too.