Booklet Creep Calculator
How far the centre pages of a saddle-stitched booklet push out past the cover, from the page count and the paper caliper, and how much to shift the pages on any sheet.
Result
Enter paper caliper (thickness of one sheet) to see the result.
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How to use the Booklet Creep Calculator
- Enter the number of pages, counting every printed side and the cover when it is the same paper.
- Enter the caliper of one sheet from the paper maker's specification, or measure a stack and divide by the number of sheets.
- Read the total creep, which is how far the centre spread sits out past the cover after folding.
- To set up a particular sheet, enter its position counted from the outside and read its shift and the pages it carries.
The formula
sheets = pages ÷ 4 (rounded up to a whole sheet)total creep = caliper × (sheets − 1)shift for sheet k = caliper × (k − 1), k = 1 for the outermost sheetpages on sheet k = 2k − 1, 2k, N − 2k + 1, N − 2k + 2 (N = pages)Each folded sheet carries four pages: two on the front half and two on the back. In a 48-page booklet the outer sheet holds pages 1, 2, 47 and 48, the next holds 3, 4, 45 and 46, and so on to the centre spread.
Why the pages move
A saddle-stitched booklet is a stack of sheets folded together and stapled through the fold. Each sheet has to bend around all the sheets inside it, so the inner sheets reach a little further from the spine than the outer ones. When the face is trimmed straight, the inner pages lose more paper. Without a correction, page numbers and outside margins creep towards the trim as you turn to the middle.
The allowance is the same idea whatever the software calls it: creep, shingling or push-out. The page takes the spreads-based form, one caliper for every sheet inside the cover. A trade article from a US printer works a 48-page book on 0.005 in stock to 0.055 in by exactly this rule, and a 2025 PrintPlanet post gives the same count as (pages − 4) ÷ 4.
Limits
- A heavy cover, coated stock and tight folds all change the real figure. The calculation is a starting point; a folded, trimmed dummy is the test.
- Very thick booklets often go perfect bound instead, where creep does not arise.
- A page count that is not a multiple of four is padded with blank pages, and the note says how many.
What the diagram shows
The sheets seen edge on, nested at the spine fold. Each inner sheet reaches further out than the one around it; the gap between the dashed lines is the total creep, printed below in your units. At most ten sheets are drawn, and the step is exaggerated so it can be seen.
With your numbers
- Sheets = 48 pages ÷ 4 = 12; the outer sheet sets the trim and does not move
- Total creep = 0.005 in × (12 − 1) = 0.055 in
Quick reference
Creep grows by about one caliper per sheet. Folding and stock vary, so a folded, trimmed dummy is the check before a long run.
| Example | Total creep at the centre spread |
|---|---|
| 48 pages on 0.005 in stock | 0.055 in |
| 76 pages on 0.0035 in stock | 0.063 in |
| 64 pages on 0.004 in stock | 0.06 in |
| 16 pages on 0.004 in stock | 0.012 in |
| 32 pages on 0.1 mm paper | 0.7 mm |
| 96 pages on 0.08 mm paper | 1.84 mm |
| 24 pages on 0.12 mm paper | 0.6 mm |
Common questions about the Booklet Creep Calculator
- Why pages ÷ 4 − 1 and not pages ÷ 4?
- Both are quoted in print forums. The outermost sheet wraps all the others, and the trim is set to it, so it moves by nothing. Each sheet inside sits one caliper further out, so a 12-sheet booklet has 11 steps, not 12. The pages ÷ 4 version adds one caliper that no sheet actually moves by; on thin stock the difference is a few thousandths of an inch.
- Which way do I shift the pages?
- Towards the spine. Inner pages stick out further at the face, so after trimming they lose more of their outside margin. Moving each sheet's content inward by its shift keeps the margins even through the whole booklet. Imposition software usually takes the total and spreads it across the sheets for you.
- What is caliper and where do I find it?
- The thickness of one sheet. Paper makers publish it on the specification sheet, in thousandths of an inch (points) or in microns. Two papers of the same basis weight can differ, so use the figure for the stock you are printing on, or measure: a stack of 100 sheets divided by 100.
- Does a heavier cover change the result?
- Yes, a little. This page treats every sheet as the same stock, which is right for a self-cover booklet. A separate cover on thicker board pushes every inside sheet out by its own extra thickness, which the page does not add. A folded dummy of the real stock shows the true figure.