Spine Width Calculator

Work out spine width instantly with clear inputs, formula shown and shareable results.

About Spine Width Calculator

The text block thickness is pages divided by the paper's pages-per-inch bulk, converted to millimetres, with cover board added on each side. Getting the spine wrong by a millimetre wraps the front cover artwork around the edge, which is why printers publish a pages-per-inch figure for every stock.

Formulas

Spine width

spine = pages / pages per inch x 25.4 mm + 2 x cover thickness

Cover width

flat cover width = 2 x trim width + spine width

Worked example

With the default values below, Spine Width Calculator returns Spine width of 21.320. Change any input above and every figure here is recalculated in your browser.

Inputs used

Page countminimum 2: 320
Paper bulk in pages per inchminimum 50: 400
Cover board thickness each sideminimum 0 mm: 0.5 mm
Trim width for the coverminimum 1 mm: 129 mm

Results

Spine width: 21.320 mm
Spine width in inches: 0.8394 in
Total flat cover width: 279.32 mm
Text block thickness without covers: 20.320 mm

Step by step

1Values used
2Spine width
3Cover width
4Spine width= 21.320 mm
5Spine width in inches= 0.8394 in
6Total flat cover width= 279.32 mm
7Text block thickness without covers= 20.320 mm

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Spine Width figure worked out?

spine = pages / pages per inch x 25.4 mm + 2 x cover thickness. The text block thickness is pages divided by the paper's pages-per-inch bulk, converted to millimetres, with cover board added on each side.

Why does this matter?

Getting the spine wrong by a millimetre wraps the front cover artwork around the edge, which is why printers publish a pages-per-inch figure for every stock.

What do I need to enter?

Enter page count, paper bulk in pages per inch, cover board thickness each side, trim width for the cover. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.