Spine width calculator
Exact spine width and full cover size for any page count.
Spine width
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Full wrap cover — the file you upload
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How the number is worked out
Spine width is page count multiplied by the thickness of a single sheet. KDP publishes one figure per paper stock, and those are the figures above — nothing is rounded or guessed.
spine = pages × thickness
width = bleed + trim_width + spine + trim_width + bleed
height = bleed + trim_height + bleed
width = bleed + trim_width + spine + trim_width + bleed
height = bleed + trim_height + bleed
Bleed is 0.125 in on the top, bottom and both outer edges. It is not added between the covers and the spine, which is why the width formula only adds it twice.