What is trim size?

In plain terms: trim size is the width and height of a finished printed page — what you'd measure if you held the paperback in your hands.

The name comes from printing: large sheets are printed and then trimmed down to the final page size. A common novel trim is 5″ × 8″ or 5.5″ × 8.5″.

When it matters

Trim size only affects the print PDF. Your EPUB has no fixed page size — the text reflows to whatever screen the reader uses — so trim size is ignored for e-books.

Choosing one

• Match your genre. Bookbndr lists the sizes readers expect for fiction, non-fiction and so on.
• Check your printer. Each size shows which print services support it (KDP, IngramSpark, Lulu). Pick one your chosen service offers.
• Bigger pages = fewer pages (and a slimmer spine), which can affect printing cost.

→ To set it: Set page size & margins.