In the not-so-long-ago days of publishing, I used to provide a worksheet to authors we coached for calculating the approximate number of pages their book would be. You can still find calculators online and formulas for using word count to figure out approximately how many book pages your manuscript will become.
Word- and page-count are important numbers to know. The number of words in you manuscript defines whether it is a novel or a novella. The number of words may also indicate that you need to beef up your story or do a whole lot of editing. And, of course, how much it costs to produce your book directly influences how you will need to price it.
But word-count is only a small part of the calculation for page-count. Some of the other factors you need to consider are:
Trim size is final width and height of your book’s pages. Research what size other books like yours are at your local bookstore to get an idea of what you want yours to look like.
The white space between the text block and the edge of the page can vary. See what other books do and decide how you want yours to look.
Font Style and Size
Some font styles take up more space than others and a twelve-point font takes more space than an eleven-point font. Keep in mind, however, that larger fonts are easier to read.
Two common paragraph styles are to insert a space between every paragraph or to indent each new paragraph and have no extra space in between. There are also variations of these two. Take a look at other books during your research trip to decide the style you like best.
Book pages that might not be part of your current manuscript include the title page, copyright page, table contents, appendix, index, graphic images and other add-ons. Also, if you are using chapter titles and starting chapters on the right side of a double page spread, your book will have more blank space
If you are publishing with Amazon’s KDP, these book design decisions are yours to make and they offer a series of videos to help you format your manuscript for publication. Since they base this tutorial on users of Microsoft Word, you could technically set up your manuscript margins, type size, etc. while you are still writing and see how your manuscript will look as a book even before it’s finished.
Since the number of pages in your book helps determine the cost to produce it, it might be worth your while to play around with the layout and design to reduce the page number. But keep in mind the overall experience you want your reader to have. Appearances are important to setting the stage for a great read!