Calculate a spine width and build a cover template
A perfect-bound cover is one flat piece: front cover, spine and back cover side by side. How wide the spine is depends on the body paper and the page count.
Load a file to start.
No upload — everything runs in your browser
The formula
Spine = leaves x sheet thickness + 2 x cover thickness, where leaves is half the page count because each sheet carries two pages. A hundred pages on 90 kg woodfree stock at 0.115 mm per sheet is 50 x 0.115 = 5.75 mm; a 180 kg coated cover at 0.19 mm adds 0.38 mm for 6.13 mm, which rounds up to 6.5 mm.
Every printer has its own thickness table
The per-sheet figures here are the nominal values the Japanese trade quotes. Real stock varies by brand and by production run, and many printers publish their own conversion table or spine calculator. If you are putting type on the spine, confirm the number with the shop before you commit. Bleed, trim marks and paper thickness differ from printer to printer — always check the spec sheet of the shop you are submitting to.
What the template contains
Pick a finished size and a binding edge and you get a single landscape page: front cover, spine and back cover in a row, with the trim outline, dashed guides at both spine folds, bleed, and trim marks if you want them. Right-bound books put the front cover on the left of the flat sheet; left-bound books put it on the right. Below about 3 mm of spine, skip spine type and wrap the cover art around instead.
Vocabulary: C1 to C4, and the kg on the paper
Japanese covers are numbered: C1 is the front, C2 its inside, C3 the inside back and C4 the back cover. Paper is sold by renryo — the weight in kilograms of a thousand sheets at the shiroku reference size — so a bigger number means thicker paper, though only within the same paper type.
Frequently asked questions
Does a saddle-stitched book have a spine width?
No. It is folded and stapled, so there is no flat spine to measure. This calculation is for perfect binding.
Why round up to half a millimetre?
Because printers quote and fold in half- or whole-millimetre steps. Rounding down moves the fold onto the front cover and pulls the front artwork around onto the spine.
Can it typeset the spine text?
No — the template carries guides only. Open the exported PDF in Illustrator or Clip Studio and set the type inside the spine area. Below about 5 mm of spine, spine text is barely legible anyway.