Bookbinding Signature Calculator
Signatures, blank pages and push-out for a folded book — where a bigger signature wastes more paper, not less.
Caliper is the thickness of one sheet, which is not the same thing as its weight in grams per square metre — bulky papers are thicker per gram than smooth ones. Measure a stack of a hundred sheets and divide, or take the figure from the paper's own datasheet. Nothing is uploaded.
A bigger signature wastes more paper, not less
One folded sheet is four pages, so every signature is a multiple of four — and whatever the last one cannot fill gets printed blank. Folding 200 pages into 16s costs 8 blank pages; folding the same book into 32s costs 24. Bigger signatures are fewer to sew and more to throw away.
| Pages per signature | Sheets | Signatures | Blank pages | Spine |
|---|---|---|---|---|
| 8 | 2 | 25 | 0 | 0.4 mm |
| 16 | 4 | 13 | 8 | 0.8 mm |
| 24 | 6 | 9 | 16 | 1.2 mm |
| 32 | 8 | 7 | 24 | 1.6 mm |
| 48 | 12 | 5 | 40 | 2.4 mm |
| 64 | 16 | 4 | 56 | 3.2 mm |
The waste can never reach a whole signature — if it did, you would simply use one fewer. And a page count that divides exactly costs nothing at all: 192 pages in 32s comes out perfectly even, while 200 wastes 24. That is why printed books so often run to lengths that look arbitrary. They are not arbitrary; they are multiples.
And the inner pages stick out, by exactly one caliper per sheet
Nested sheets do not share a spine. Each one folds around the sheets inside it, so its fold sits one paper thickness further out than the next — and since every leaf is the same length, the innermost fore edge protrudes past the outermost by one caliper for every sheet enclosing it. A 64-page signature in 0.1 mm paper pushes out 1.50 mm.
| Paper | Caliper | Push-out, 32-page signature |
|---|---|---|
| Thin bible paper | 0.04 mm | 0.28 mm |
| Light book paper | 0.08 mm | 0.56 mm |
| Ordinary book paper | 0.1 mm | 0.70 mm |
| Heavy text paper | 0.15 mm | 1.05 mm |
| Card or watercolour | 0.3 mm | 2.10 mm |
That protrusion gets trimmed off at the fore edge, which means the inner pages of every signature end up narrower than the outer ones. On bible paper it is 0.28 mm and nobody notices; on card it is 2.10 mm and a margin that ignored it will not survive the guillotine. A useful check on any figure: the push-out is always less than the spine thickness, because it is one caliper per sheet against two.
How to use
- Enter the page count of the book.
- Enter the pages per signature, a multiple of four.
- Enter the paper caliper in millimetres.
- Read the signatures, the blanks and the push-out.
Frequently asked questions
How many pages are in a signature?
A multiple of four, because one folded sheet gives two leaves printed on both sides. Sixteen and thirty-two are the common sizes; the sheet count is simply the pages divided by four.
Why does my book have blank pages at the end?
Because the page count does not divide by the signature size, and a signature cannot be part-folded. Whatever the last one cannot fill gets printed blank — 200 pages in 16s leaves 8 blanks, and the same book in 32s leaves 24.
Is a bigger signature more efficient?
Fewer to sew, but more paper thrown away. The waste can be anything up to one page short of a whole signature, so doubling the signature size roughly doubles the expected waste. It is a trade, not an improvement.
How do I avoid blanks entirely?
Make the page count a multiple of the signature size. 192 pages in 32s comes out perfectly even while 200 wastes 24, which is why printed books run to lengths that look arbitrary. They are multiples, not accidents.
What is creep or push-out?
Nested sheets do not share a spine. Each folds around the ones inside it, so its fold sits one caliper further out — and since every leaf is the same length, the innermost fore edge protrudes by one caliper per enclosing sheet.
How much does it push out?
Sheets minus one, times the caliper. A 32-page signature in ordinary 0.1 mm book paper pushes out 0.7 mm; the same signature in 0.3 mm card pushes out 2.1 mm. It grows with both the signature size and the paper thickness.
Does that matter for my layout?
It does once it exceeds your margin tolerance. The push-out is trimmed off at the fore edge, so the inner pages of every signature end up narrower than the outer ones. A quick sanity check: push-out is always less than the spine thickness.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.