Why spine width comes first
Spine width is the first dimension to lock down before any cover artwork starts. Set it too wide and the title drifts onto the front board; set it too narrow and the spine color wraps around the edges. Total page count plus the caliper of one leaf is all you need.
How it is calculated
This uses the formula published by commercial book printers. One leaf carries two pages, so the leaf count is half the page count, multiplied by the caliper of a single leaf. With pages per inch, the page count is divided by PPI to give inches directly. Perfect binding adds the two cover boards on top. Current as of October 2026.
Limits and disclaimer
Bulk varies by 10 to 20 percent at the same basis weight, so converting paper weight to thickness is not supported. Adhesive thickness, drying shrinkage and binding-specific allowances are not included either. Confirm the final figure with your printer before sending files.
Frequently Asked Questions
Ask your printer or paper merchant for the caliper or the pages-per-inch figure. Bulk varies by 10 to 20 percent at the same basis weight, so paper weight alone cannot give you a thickness.
One leaf carries two pages, so the leaf count is rounded up and the result shows a rounding note only when that rounding actually happened.
Perfect binding adds the front and back covers to the text block. The caliper you enter for one cover is multiplied by two; leave it blank to see the text block alone.