Data changelog

Every change to a stored value, with the date and the reason. A correction here propagates to every page computed from that value.

Initial data set published

2026-08-08 · Launch

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.

Spine formula published without the 0.06" constant

2026-08-08 · Correction

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.

How re-verification works

Fee schedules are re-checked against their official source on a fixed cycle, and the build fails if any goes past its window. Physical standards are checked quarterly. When a check changes a stored value, an entry is appended here automatically with the old and new figures.