Quick answer
For a PUR perfect-bound book, the spine width is roughly inside pages ÷ 2 × paper thickness, plus the cover. Thickness is about one micron per gsm, so 64 inside pages of 250gsm make a spine of about 8mm before the cover. For a saddle-stitched booklet there is no spine to measure, but the page count must be a multiple of four, including the cover. Use the calculator for an estimate, then design the cover to the spine width we confirm from the actual stock.
Key takeaways
- Saddle-stitched books are built from folded sheets of four pages, so 8, 12, 16, 20… pages including the cover.
- Perfect-bound spine width = inside pages ÷ 2 × paper caliper, plus the cover board on each side.
- Gsm is only a proxy for thickness. A caliper from the paper's data sheet gives a more accurate answer.
- Always set the final cover artwork to the spine width your printer confirms.
Spine width & page count calculator
Booklet page count & spine width calculator
Estimated spine width
≈ 4.8 mm
Inside pages plus a wraparound cover. Use it to plan the cover layout, then design to the width we confirm from the actual stock.
Inside pages only
4.2 mm
32 leaves × 130 microns.
Spine width = inside pages ÷ 2 × paper thickness. When you enter a weight, thickness is estimated at one micron per gsm, the rule of thumb used in our binding guide. Real stocks vary, uncoated and bulky papers especially, so treat the result as an estimate.
Page counts for saddle stitching
A saddle-stitched booklet is made from sheets folded in half and stapled through the fold. Each folded sheet gives four pages, so the total, cover included, is always a multiple of four. If the content comes to 22 pages, plan for 20 or 24: tighten the copy, or add a contents page, notes page or ad. As books get thicker, the inner pages push outwards at the fore-edge (creep), which the binding methods guide explains.
| Pages (incl. cover) | Folded sheets | Works for saddle stitching? |
|---|---|---|
| 8 | 2 | Yes |
| 12 | 3 | Yes |
| 14 | 3.5 | No: use 12 or 16 |
| 16 | 4 | Yes |
| 22 | 5.5 | No: use 20 or 24 |
| 32 | 8 | Yes |
Working out a perfect-bound spine
- 1
Count the leaves
Halve the number of inside pages. A 96-page book has 48 leaves.
- 2
Find the paper thickness
Use the caliper in microns from the paper's data sheet. If you only know the weight, one micron per gsm is a reasonable first estimate.
- 3
Multiply
48 leaves × 130 microns = 6,240 microns, or about 6.2mm.
- 4
Add the cover
The cover wraps round both sides of the book block, so add its thickness twice. A 300gsm cover adds roughly 0.6mm.
Confirm before you finalise the cover
Uncoated and bulky papers can be much thicker than their weight suggests, and the difference adds up across a book. Lay out the cover with the spine as a separate panel so it is easy to adjust once we confirm the width. Our artwork set-up guide covers bleed and print-ready PDFs.
Booklet printing
Saddle-stitched and PUR perfect-bound booklets for reports, programmes, manuals and magazines.
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