Will your title fit the spine?
Lettering a spine fails two ways: too narrow a spine, where binding drift rolls the type off the edges whatever its size, and too long a title, where the type shrinks below reading. This checks both — the quarter-inch floor from the same model as the spine calculator, and the type arithmetic for your exact title — and names the largest size that survives both. Before the foil order, not after.
Count it as it prints — spaces are advances too.
- Largest honest size
- 6.4 ptworks, but check it on a proof before foil
- Binding floor
- clearedlettering needs 6.35 mm of spine; below it, drift eats the type
- Page floor
- clearedprint-on-demand floors start at 80 pages, whichever is wider
Advance widths are averages — kern a real proof before committing to foil or deboss. The arithmetic runs on this machine.
The two floors
- 6.4 mm of spine (a quarter inch) — below it, bindery drift eats the lettering regardless of arithmetic. Lettering that rolls onto the covers looks like exactly the mistake it is.
- 80 pages at print-on-demand — Lulu's floor is 80 pages, whichever of spine-width or page-count binds first. KDP's differs; use theirs for theirs.
- And the fit itself — characters × average advance at a size, against the spine in points. Mixed case averages ≈0.55 em; ALL CAPS run ~13% wider and the tool charges for it.
Questions people actually ask
How accurate is the point size?
It uses 0.55 em as the average advance of mixed-case title type — a measured middle. Kerning, condensed faces and long runs of caps all move it. Treat the number as the honest ceiling and set the real size on a proof.
What about reading direction on the spine?
English-language tradition: top-to-bottom when the book stands face-out (US) or bottom-to-top (European). Pick one and hold it across the whole run — mixed directions on a shelf is the fastest way to look self-published.
Foil, ink, or deboss?
Foil survives handling best on cloth; ink on paper spines wants at least 10 pt to hold; deboss without fill is subtle to a fault on dark cloth. All three need the same fit arithmetic first.
Does this work for hand-lettered spines?
Type the title in its final spelling and count every character including spaces — hand-lettering obeys the same spine. If your lettering is wider than Helvetica per character, knock a point off the answer.
The studio letter spines from the same arithmetic it sizes them with.
Make the book — freeThis is one of the tools — or see everything we’ve written.