Book spine calculator
A paperback spine is its page count multiplied by the thickness of one sheet of the paper it is printed on. That figure is different for white, cream and premium colour, and it is the reason most self-published covers come back.
Free, no signup, and the working is shown so you can check it against your printer’s own page.
412 pages × 0.0025″ per page = 1.0300″
1.0300″ × 25.4 = 26.16mm
0.0025″ is Amazon KDP’s published figure for cream paper. Check it on their page before you send artwork.
- Flat sheet, with bleed
- 337.3 × 234.9 mm
- Each cover, trimmed
- 152.4 × 228.6 mm
- Spine starts at
- 155.6 mm
- Bleed, every edge
- 3.175 mm (0.125″)
- Keep clear for the barcode
- 50.8 × 30.5 mm
The spine is wrong
The one above. Two millimetres out and the front artwork creeps around the fold, or the spine type sits off-centre. It is the commonest rejection and the easiest to avoid.
Type on a spine too narrow for it
Under 79 pages, Amazon KDP requires a blank spine and rejects a cover with the title on it. Under 24 pages there is no perfect-bound spine at all.
Artwork under the barcode
The printer prints the ISBN barcode over whatever is there. A 50.8 by 30.5mm area at the bottom right of the back cover has to be kept clear.
If you would rather not lay the wrap out yourself, our book covers take the page count and the paper as editable fields and redraw the spine as you change them, with the barcode area and the bleed already in place.