This is asked constantly and answered badly, usually with a single number and no mention of the four things that determine it. So here is the number, then the arithmetic, so you can work out your own rather than trusting mine.
The working figures
| Page | Type | Words per page |
|---|---|---|
| A4, 11pt, 25mm margins | Serif body, 1.4 line spacing | 450–500 |
| A4, 12pt, 25mm margins | Serif body, 1.5 line spacing | 380–420 |
| Trade paperback 6×9in | 11pt, standard margins | 280–320 |
| Mass-market paperback | 10pt, tight margins | 250–280 |
| A5 workbook | 11pt, room to write | 200–250 |
| Double-spaced manuscript | 12pt Courier or similar | ≈250 (by convention) |
The last row is a different kind of number and worth flagging. "250 words a page" is a publishing convention from the typewriter era, used so that everyone could agree on a length before anyone typeset anything. It is not a measurement of a real page and it should not be used to estimate a printed book.
The arithmetic, if you want your own number
Words per page is lines per page multiplied by words per line. Both are calculable.
Lines per page is the height of the text area divided by the line height. An A4 page is 297mm tall; take 25mm of margin off the top and bottom and you have 247mm of text. At 11pt type with 1.4 line spacing, each line occupies about 15.4pt, which is about 5.4mm. That gives roughly 45 lines.
Words per line follows from the measure — the width of the text column. A comfortable line holds 60 to 75 characters, and English averages about 5.7 characters a word including the space after it. So a 66-character line is about 11 words.
lines per page = text height / line height
words per line = characters per line / 5.7
words per page = lines x words per line
A4, 11pt, 1.4 spacing, 25mm margins:
45 lines x 11 words = ~495 words per pageWhich is where the 450 to 500 in the table comes from. Change the type size to 12pt and the leading to 1.5 and you lose about eight lines a page — the same manuscript grows by roughly a sixth without a word being added.
What actually moves the number
- Type size. The single biggest lever. A point of body size is worth 8 to 10 percent of your page count.
- Line spacing. Going from 1.3 to 1.5 costs you around 13 percent of your lines.
- Margins. Generous margins are correct — they are what makes a page look like a book — and they cost pages. Budget for that rather than tightening them to hit a number.
- Trim size. A 5×8in page holds a little over half what an A4 page holds. This is why the same manuscript is a 200-page paperback and a 120-page PDF.
- Chapter openings. If every chapter starts on a fresh page, a book of 30 short chapters carries up to 30 part-empty pages. On a print-on-demand title that is real money.
- Images, tables and code. These break the estimate entirely. A book with a figure every other page cannot be estimated from a word count at all.
Typical lengths, by what you are writing
| Kind of book | Words | Pages (trade paperback) |
|---|---|---|
| Lead magnet or short guide | 2,000–5,000 | 8–20 at A4 |
| Novella | 20,000–45,000 | 80–170 |
| Standard novel | 70,000–100,000 | 270–390 |
| Business or self-help nonfiction | 40,000–70,000 | 160–270 |
| Memoir | 70,000–100,000 | 270–390 |
| Technical or reference | 60,000–120,000 | Varies — figures dominate |
| Children's picture book | 500–1,000 | 32 (a fixed convention) |
Two of these have hard edges rather than preferences. Picture books are 32 pages because of how sheets are folded and cut, and a debut novel much past 120,000 words is a harder sell to an agent regardless of its quality. The rest are ranges, and being outside one is a question to answer, not a rule you broke.
Page count has consequences
It is not only an estimate to satisfy curiosity. Three things downstream depend on it:
- Print cost. Print-on-demand prices are per page, so page count sets your unit cost and therefore your minimum viable price.
- Spine width. The spine of a printed cover is page count multiplied by a paper-thickness figure. Get the count wrong and the cover artwork is wrong — see cover dimensions for how that fits together.
- Inside margins. Thicker books need a wider gutter, because more of the inner margin disappears into the binding. Printers publish this as a table against page count.
The only estimate worth trusting
Set the type the way the book will actually be set, export it, and look at the last page. Everything above is for planning before you have anything to look at; once you do, the estimate is obsolete.
This is the practical argument for a preview that paginates while you write. If the page count only appears at the end of an export-and-check cycle, you find out that trimming a point of body size would have saved fourteen pages at the point where re-typesetting is a chore. bukpress repaginates as you type, so the count is a thing you watch rather than a thing you discover — and the sample book is what a finished eight-page one looks like.