Trim size is the finished width and height of your pages. It sounds like a minor technical choice, but it shapes almost everything else: how many pages your book has, how the text feels to read, what it costs to print and even how the book is perceived on a shelf. It is best decided early, because your interior layout and your cover both depend on it.

Start with what readers expect

Most genres have familiar sizes. Many novels use compact sizes that fit comfortably in the hand. Non-fiction and business titles often use slightly larger formats, which suit headings, lists and diagrams. Workbooks and journals tend to be larger still, because readers need room to write. Picture books follow their own conventions, often square or landscape.

Look at five or six recent bestsellers in your category and note their dimensions. You do not have to match them, but you should know when you are deviating. A fiction paperback in an unusual large format can feel more like a textbook, which may not be the impression you want.

Consider page count and spine width

A larger page holds more words, so the same manuscript will produce fewer pages. A very short book can look thin and flimsy, while a very long one can become heavy and expensive. Page count also determines spine width, which affects whether you can print a title on the spine at all. Very thin books often cannot carry spine text legibly.

That is why we recommend choosing trim size before you finalise the cover. Our interior layout service and cover design service use your final page count to build files that fit exactly.

Paper: white or cream, and why it matters

Print-on-demand platforms usually offer at least two paper colours. Cream paper is often chosen for fiction and memoir, because it is gentler on the eyes over long reading sessions and gives a classic feel. White paper is common for non-fiction, textbooks and anything with images or diagrams, because it gives crisper contrast and more accurate colour.

Paper weight also affects thickness and feel. Heavier stock feels more substantial but increases spine width and cost.

Think about cost

Print-on-demand cost depends on page count, trim size, paper, ink type and binding. Colour interiors cost significantly more than black and white. Before choosing a format, use the platform's own cost calculator with your expected page count to see what the unit cost will be and whether your intended price still leaves you a sensible margin.

A simple decision checklist

  1. Note the common trim sizes in your genre.
  2. Estimate your page count at two or three candidate sizes.
  3. Check printing cost for each option on your chosen platform.
  4. Decide on paper colour based on genre and the content of your pages.
  5. Lock the choice, then format your interior and design your cover to match.

Where to go from here

If you are unsure, ask us. We can recommend sizes for your genre, show sample pages at different trim sizes and explain the cost impact before you commit. Getting this decision right at the start saves rework later.