Part of: KDP Publishing Guide: Low-Content Books · KDP low-content publishing
This KDP cover calculator gives the exact spine width and full cover size KDP expects: enter page count, paper type and trim size, verified against Amazon's published formula.
Template guides: red = bleed (trimmed off), blue = spine, dashed = keep text inside, grey box = barcode area to keep clear. Hide or delete the guide layer before you upload your finished cover.
KDP cover size = 0.125" bleed + back cover width + spine + front cover width + 0.125" bleed, and height = trim height + 0.25". Spine width is page count × 0.002252" for white paper, 0.0025" for cream or 0.002347" for premium colour. A 120-page 6×9 white-paper book needs a 12.52" × 9.25" cover.
A KDP paperback cover is one flat image that wraps around the book: back cover on the left, spine in the middle, front cover on the right, plus bleed on all four edges. The calculator above does the arithmetic; this is what it is doing, so you can sanity-check any result.
Width = 0.125" bleed + trim width + spine width + trim width + 0.125" bleed
Height = 0.125" bleed + trim height + 0.125" bleed
Spine width = page count × paper factor
Worked through for a 120-page, 6" × 9", white-paper journal:
Insight: The paper factor is the number people get wrong, not the arithmetic. Cream paper is about 11% thicker per page than white, so a 300-page book is 0.676" wide on white and 0.750" on cream — enough to push spine text onto the cover if you design for one and print on the other.
Every trim at 120 pages on white paper (spine 0.270"), with bleed included:
| Trim | Spine | Full cover (inches) | At 300 DPI |
|---|---|---|---|
| 5" × 8" | 0.270" | 10.520" × 8.250" | 3,156 × 2,475 px |
| 5.5" × 8.5" | 0.270" | 11.520" × 8.750" | 3,456 × 2,625 px |
| 6" × 9" | 0.270" | 12.520" × 9.250" | 3,756 × 2,775 px |
| 7" × 10" | 0.270" | 14.520" × 10.250" | 4,356 × 3,075 px |
| 8.5" × 11" | 0.270" | 17.520" × 11.250" | 5,256 × 3,375 px |
For a different page count, keep the trim columns and recompute only the spine: each extra page adds 0.002252" on white paper.
| Paper / ink | Inches per page | 100 pages | 200 pages | 300 pages |
|---|---|---|---|---|
| Black ink, white paper | 0.002252" | 0.225" | 0.450" | 0.676" |
| Black ink, cream paper | 0.0025" | 0.250" | 0.500" | 0.750" |
| Premium colour, white paper | 0.002347" | 0.235" | 0.469" | 0.704" |
White paper is the default for journals, planners and logbooks because it shows lines and dot grids crisply. Cream suits novels and poetry, where readers expect a softer page.
KDP's help page says a book needs "at least 79 pages" for spine text — and in another paragraph, "more than 79". Its own Cover Creator requires 80. The calculator flags eligibility at 79; if you want certainty, design for 80 pages.
When you do add spine text:
The interior has its own rules — the inside (gutter) margin grows with page count, because thicker books curve more at the binding:
| Page count | Inside margin | Outside margin (no bleed) | Outside margin (with bleed) |
|---|---|---|---|
| 24–150 | 0.375" | 0.25" | 0.375" |
| 151–300 | 0.5" | 0.25" | 0.375" |
| 301–500 | 0.625" | 0.25" | 0.375" |
| 501–700 | 0.75" | 0.25" | 0.375" |
| 701–828 | 0.875" | 0.25" | 0.375" |
Designing at trim size. A 6" × 9" front cover file is not a KDP cover. Upload the full wrap at the size the calculator gives, or KDP rejects it.
Changing paper after designing. Switching a 300-page book from white to cream adds 0.074" to the spine. Everything shifts; recalculate and re-export.
Text in the bleed. "Looked fine on screen" is the most common complaint after a first proof. If any letter sits within 0.125" of the trim, move it.
Low-resolution artwork. A 1,200-pixel-wide image stretched across a 6" front cover is 200 DPI. It uploads, then prints soft. Start from artwork at least 1,800 px wide for a 6" cover.
The cover is the last step. Before it come the trim size and the interior page count, and after it the price:
For the whole process, read the KDP publishing guide. Craftific's KDP tools generate interiors at spec-correct margins for every trim size, so the page count you calculate with here is the page count you upload.
Multiply the page count by KDP's paper factor: 0.002252" per page for white paper, 0.0025" for cream and 0.002347" for premium colour. A 200-page book on white paper has a 0.450" spine; the same book on cream is 0.500".
KDP's help page says at least 79 pages, but it also says "more than 79" in another place, and its Cover Creator requires 80. Plan for 80 pages if you want spine text, and keep the text 0.0625" away from each spine edge.
300 DPI. At that resolution a 12.52" × 9.25" cover is 3,756 × 2,775 pixels. Lower resolutions upload but print soft, and KDP's previewer flags images under 300 DPI.
Usually one of three things: the PDF is the trim size instead of the full bleed size, the spine was calculated for the wrong paper type, or text sits closer than 0.125" to the trim. Recalculate with the page count and paper type you actually uploaded — changing paper after designing the cover is the most common cause.
Yes. Every page changes the spine by about 0.002", so adding 20 pages to a white-paper book widens it by 0.045" and shifts both covers. Finalise the interior page count before you design the cover.
It uses the same published formulas — paper factors, 0.125" bleed, spine text clearance and barcode area — so the dimensions match. Check the final PDF in KDP's own previewer before publishing; it is the last word.
Only if you set a custom canvas to the exact full-cover size from this calculator — for example 12.52" × 9.25" for a 120-page 6×9 — and export a print PDF. Canva will not adjust the spine for you, so rebuild the canvas whenever the page count changes.
Generate a cover sized exactly to your spine width and trim size — no manual math required.
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