Spine width is simply the thickness of your text block: page count multiplied by the thickness of a single page. Get it wrong and your title wraps onto the front cover — or the printer rejects the file.
How spine width is calculated
Two methods are used in practice. The physical method multiplies sheet thickness by the number of sheets; this calculator derives single-page thickness from paper weight (GSM) and bulk, which is how printers outside the US usually quote it. The per-page method multiplies the page count by a fixed thickness per page, which is how Amazon KDP and most print-on-demand services publish their numbers.
Per-page thickness, common stocks
| Paper | Per page | 200-page spine |
|---|---|---|
| KDP white | 0.0572 mm | 11.4 mm / 0.450 in |
| KDP cream | 0.0635 mm | 12.7 mm / 0.500 in |
| Offset 80 gsm | 0.052 mm | 10.4 mm / 0.41 in |
| Bulky novel 80 gsm | 0.072 mm | 14.4 mm / 0.57 in |
Binding types and the spine
- Perfect bound (paperback) — a flat glued spine; this is where spine width matters most.
- Hardcover (case bound) — the cover wraps a rigid board, so the template adds wrap and hinge allowances around the text-block spine.
- Saddle-stitched — folded and stapled, so there is no flat spine and no spine text.
Can I print text on the spine?
Most print-on-demand services need roughly 80 pages (a spine of about 3 mm) before they allow spine text, to avoid it creeping onto the covers. Below that, keep the spine blank.
Building the cover
A full cover is one flat spread: back cover, spine, front cover, plus bleed on the outer edges. Extend any background all the way into the bleed, keep text inside the safe area, and align nothing critical with the fold lines. Export the template, place it as a locked guide layer, and design on top.