Cover Board Calculator

Cutting cover boards to the wrong size is one of the fastest ways to ruin an otherwise good case binding, so this calculator applies the two standard bookbinding rules directly to your book block dimensions. Board height adds the overhang (the "squares") to both the top and bottom of the block — board height = block height + (2 × overhang) — because the board needs to protect the block's edges on every side except the spine. Board width only adds the overhang once, since the spine edge of the board sits flush against the block with no overhang there at all; only the fore-edge gets the protective lip. A 3 mm (1/8 in) overhang is the long-standing default for most trade-size books, though the tool lets you dial it from 1 to 10 mm for miniature or oversized work.

It also recommends a davey board thickness purely from block height — under 180 mm gets 1.5 mm board, up to 260 mm gets 2.0 mm, up to 350 mm gets 3.0 mm, and anything larger gets 4.0 mm — because taller books need stiffer boards to resist warping and to support their own weight when shelved. Results are given in both millimeters and inches, and the total board area is computed across two boards per book (front and back cover) times however many books you're binding, which is the number you actually need when buying davey board or binder's board by the sheet. Keep in mind the thickness figures are a starting guideline, not a structural calculation — very heavy paper stock, vellum-covered boards, or unusually large formats may still call for a heavier board than the default recommendation.