A novelist of my acquaintance insists that the only way to estimate the number of words in a book is to multiply the number of pages by 250.
That was the formula in the good old days when Courier was the only typeface and typewriters were King.
Now we have computers and word processing software. It’s no longer necessary to estimate according to the 250-words-per-page formula. All we have to do is use the WP tool that shows Word Count.
Publishers want to know the overall length of your book. An approximate word count (round numbers) based on what your WP tells you enables them to estimate costs and other factors involved in printing a book.
Novels for adult readers fall between 80,000 and 120,000 words. A novel of 50,000 would be the absolute minimum for some genres and, unless you are Ken Follett or some other established author, you should view 100,000 as the maximum. (Yes, exceptions for a first novel can be found, but writers who depend upon being The Exception are handicapping themselves unnecessarily.)
Every genre has its own length preferences. Novels intended for the adult market will be longer than those targeted at children and young adults. A young adult novel will run between 20,000 and 40,000 words. In terms of adult mainstream fiction, that length would be considered a novella.
TIP: Don’t compose your novel with skinny margins, single-spacing and some off-the-wall font and then make formatting changes when you’re ready to market the completed manuscript.
Draft your novel in standard format from the start:
12-point Times Roman or 12-point Courier.
Margins set to 1-inch all round
NOTE: Don’t put extra spacing between paragraphs unless your intention is to indicate a shift of viewpoint or passage of time.
When you are ready to approach an agent or a publisher, study their guidelines carefully and submit your work exactly according to their preferences.