https://sellerspec.com/ Corrections, re-verifications and additions to the underlying data. en https://sellerspec.com/changelog/ sellerspec.com-2026-08-08-initial-data-set-published Sat, 08 Aug 2026 09:00:00 GMT 51 paper sizes across ISO A, B and C, North American, photo and planner formats. 15 book trim sizes across 4 paper stocks. Fee schedules for Etsy, eBay and Amazon. https://sellerspec.com/changelog/ sellerspec.com-2026-08-08-spine-formula-published-without-the-0-06 Sat, 08 Aug 2026 09:00:00 GMT The widely reproduced spine formula adds 0.06" to page count × paper thickness. That constant does not appear in the printer's published specification, and it makes a finished cover roughly 1.5 mm too wide. Every figure on this site is computed without it.