Per page
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Spine & Cover Wrap Calculator
One leaf = one sheet = 2 pages. Spine = pages ÷ 2 × caliper.
Recalculate after your final proofread — page counts shift on the last pass almost every time.
Spine width
— in
— mm
Pages / inch
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Paper
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Full cover wrap
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Proportional diagram — back, spine and front panels with bleed zones.
Reverse Solver — Target Spine → Max Pages
Designing to a fixed spine? Enter the spine width you need (a series look, a slipcase, a printer's maximum) and get the maximum page count each paper stock allows — rounded down to an even number, the way printers bind.
Maximum pages at 1″ spine
— pages
Exact fit: — ″ spine · headroom —″
| Paper stock | Max pages | Exact spine |
|---|
Export Workflows — Canva, InDesign, Word
Your numbers, translated into each tool's setup. Dimensions below update live from the calculator above.
- Create a design with Custom size:
—px (that's—in at 300 DPI). Canva's px field assumes 96 DPI on screen — the pixel count is what matters for print sharpness. - Turn on Show print bleed (File → View settings) and keep artwork inside the safe zone:
0.25″from every trim edge,0.0625″clear of each spine fold line. - Place spine text centered on the
—spine panel; keep it0.0625″(1.6 mm) from the fold on each side. - Share → Download → PDF Print, check Crop marks and bleed, flatten, embed fonts. Upload the PDF to KDP/IngramSpark.
Honest note: Canva can't do true CMYK or fine fold-line control. For covers with critical color matching, finish in InDesign or have your printer convert the PDF.
- New document: 1 page, page size = full wrap
—in (W × H). Intent: Print. - Bleed:
0.125″on all four sides. Slug:0.5″for job notes. - Draw vertical guides at: bleed edge
0.125″, back panel—, spine—, front panel—, bleed edge. Mark the spine fold lines as a non-printing layer. - Set spine text on its own layer, centered, with
0.0625″clearance from each fold line. Barcode: leave a2″ × 1.2″white box,0.25″from trim, bottom-right of the back panel (or let KDP place it). - Export: Adobe PDF (Print), [PDF/X-1a] or [PDF/X-4], marks: crop marks only, use document bleed settings, embed all fonts.
- Layout → Size → More Paper Sizes: set Width
—in, Height—in, orientation landscape/portrait to match. - Margins → Custom:
0.125″all sides (this is your bleed — Word has no true bleed, so extend background art to the page edge manually). - Use a 3-column table (back | spine | front) sized
—to hold the layout; remove borders. - File → Save As → PDF. Check the PDF at 100% zoom — Word rasterizes some effects.
Honest note: Word is not a prepress tool — no true bleed, weak color management, font embedding quirks. Fine for simple text covers and drafts; use Canva or InDesign for final files.
The Paper Database
Every stock the calculator offers, with its per-page thickness, pages-per-inch and source. KDP factors are KDP's own published spine measurements; offset values are a UK trade printer's published spine table; gsm estimates use a standard bulking factor and are marked as estimates.
| Paper stock | Per page | Per leaf (2 pp) | PPI | Source |
|---|
Why two numbers? Spine width is sometimes written pages × per-page thickness (KDP's style) and sometimes (pages ÷ 2) × caliper (printers' style, where caliper is the thickness of one sheet). They are the same number — per-page thickness is exactly half the leaf caliper.
Methodology — The Exact Math
Paperback (perfect bound)
This is how to calculate book spine width for any perfect-bound book — the standard book spine formula used by print-on-demand platforms:
spine = pages × perPage + const or equivalently spine = (pages ÷ 2) × caliper + const
coverW = 2 × trimW + spine + 2 × bleed · coverH = trimH + 2 × bleed (KDP's official cover equations; bleed = 0.125″)
Hardcover (case wrap) — estimate
board = trim + 2 × 0.125″ squares · spinePanel = spine + 2 × 0.098″ board · wrapW = 2 × boardW + spinePanel + 2 × 0.25″ hinge + 2 × 0.625″ turn-in · wrapH = boardH + 2 × 0.625″
Dust jacket — estimate
jacketW = 2 × flap + 2 × (trimW + 0.25″) + spine + 0.25″ · jacketH = trimH + 0.25″
Reverse solver
maxPages = floor((target − const) ÷ perPage), rounded down to an even number.
Pre-press estimate, not a proof. Paper caliper varies by mill, batch and humidity. KDP paperback factors here are KDP's own published numbers; hardcover and dust-jacket geometry are industry-standard estimates. Always verify against your printer's template — or generate KDP's official template — before approving a print run.
Questions, Answered
How do I calculate book spine width?
Multiply your final page count by your paper's per-page thickness, then add any binding constant: spine = pages × per-page thickness + constant. For example, a 300-page book on KDP cream paper (0.0025″ per page) has a spine of 300 × 0.0025 = 0.75″. The calculator above does this automatically for 11 paper stocks, and always recalculate after your final proofread — page counts almost always shift at the last pass.
How many pages per inch (PPI) is KDP paper?
From KDP's published spine measurements: white paper (black ink) is about 444 PPI (0.002252″ per page), cream paper is 400 PPI (0.0025″ per page), standard color is about 426 PPI (0.002347″ per page), and groundwood is about 426 PPI (0.00235″ per page). PPI is simply 1 ÷ per-page thickness, and the calculator shows it for every stock.
What size should my book cover be?
A paperback cover is one continuous sheet: back cover + spine + front cover + bleed on every outer edge. With KDP's 0.125″ bleed: full width = trim width × 2 + spine width + 0.25″, and full height = trim height + 0.25″. A 6×9″ book with 100 pages on cream paper (0.25″ spine) needs a 12.5 × 9.25″ cover file.
How do I calculate book cover size in pixels?
Multiply inches by your export DPI. Print-on-demand covers are built at 300 DPI, so a 12.5 × 9.25″ cover becomes 3750 × 2775 px. The calculator shows pixel dimensions at 300 DPI for every result, ready to paste into Canva's custom-size dialog.
What is the KDP cover size for a 6×9 book with 100 pages on cream paper?
Spine = 100 × 0.0025″ = 0.25″ (6.35 mm). Full cover = 2 × 6″ + 0.25″ + 2 × 0.125″ = 12.5″ wide × (9″ + 2 × 0.125″) = 9.25″ tall — 317.5 × 235 mm, or 3750 × 2775 px at 300 DPI. This matches KDP's own cover calculator.
Can I use this instead of the KDP cover calculator?
For planning and drafts, yes — the KDP paper factors here are KDP's own published numbers, so paperback results match their calculator. For the final print file, still generate KDP's official template as the last check, especially for hardcover: KDP's hardcover numbers are not derivable from any published formula, and formula-built hardcover files have been rejected.
How do I calculate spine width for IngramSpark?
IngramSpark doesn't publish a per-page thickness factor — their spine comes from their cover template generator. Use this calculator's paper database as the pre-press estimate (pick the stock closest to your IngramSpark paper choice), then confirm against IngramSpark's official template before uploading. The math is identical; only the exact caliper differs by mill.
How thick is the spine of a hardcover book?
A hardcover's printed spine panel is wider than the paperback spine for the same pages: spine panel ≈ paperback spine + 2 × board thickness (about 0.196″ for standard 2.5 mm boards), because the case material wraps around the boards. The full case also adds squares (board overhang, ~0.125″ per edge), hinge allowance (~0.25″ per side) and turn-ins (~0.625″ per side). The calculator's hardcover mode shows all of these.
How do I calculate dust jacket size?
Jacket width = 2 × flap width + 2 × (trim width + 0.25″) + spine width + 0.25″ joint ease; jacket height = trim height + 0.25″ (about 3 mm overhang top and bottom). Flaps are typically 3–4″ (76–102 mm). The dust-jacket mode above computes this with an adjustable flap width.
What is bleed and why 0.125 inches?
Bleed is extra artwork past the trim line so tiny shifts during cutting never leave a white sliver. KDP and IngramSpark both require 0.125″ (3.2 mm) on every outer edge of the cover — not just left and right, but top and bottom too. Keep important text at least 0.25″ inside the trim line.
Do blank pages count toward the spine width?
Yes. The spine is set by physical leaves, so count every page in your final interior PDF — including blank pages, front matter and back matter. If your interior file has 100 pages, use 100, even if the story ends on page 92.
What if my book has an odd number of pages?
Printers bind books in even page counts (each leaf has two sides). If your count is odd, add one blank page to make it even — the spine difference of a single leaf is a fraction of a millimetre and won't affect your cover, but the even count will keep the printer's preflight checks happy.
How many pages fit in a 1-inch spine?
Divide by the per-page thickness and round down to an even number. On KDP cream paper (0.0025″ per page), 1 ÷ 0.0025 = 400 pages. On KDP white (0.002252″), it's 444 pages. The reverse solver above does this for any target spine width and any paper stock.
Why does my printer's template show a different spine width?
Paper caliper varies between mills, batches and humidity — two ‘120 gsm uncoated’ stocks can differ by 5–10%. Published factors are averages. Treat any calculator (including this one) as a pre-press estimate and always verify against your printer's template or proof before approving the print run.
How do I set up my book cover in Canva, InDesign or Word?
Canva: create a custom-size design with the pixel dimensions shown above (300 DPI), export as PDF Print with crop marks. InDesign: new document at trim size with 0.125″ bleed on all sides, then build the cover as a single spread at the full wrap size. Word: set a custom page size to the full wrap dimensions in inches — it works for simple covers, but Word is not a prepress tool, so prefer Canva or InDesign for final files. Full step-by-steps are in the Export section.
What is the minimum spine width for spine text?
KDP prints spine text only on books with more than 79 pages, and even then the text must fit with at least 0.0625″ (1.6 mm) clearance from each spine edge. For very thin books, leave the spine blank — the calculator flags books under this threshold automatically.