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The official KDP formula uses 0.002252 inches per page for white paper, 0.0025 for cream, 0.002347 for hardcover. Enter your page count, get an exact spine width in inches, mm, and 300 DPI pixels.
The official KDP formula
Spine Width = (Page Count x Paper Thickness) + 0.06" cover allowance
White paper uses 0.002252 inches per page. Cream uses 0.0025. Hardcover case laminate uses 0.002347.
Enter page count and choose paper type.
Allowed range for this binding: 24 to 828 pages.
Most common KDP paper. Used for novels and non-fiction.
Calculation breakdown
200 x 0.002252 = 0.4504"
+ 0.06 cover allowance = 0.5104"
Print-ready values in three units.
Spine width (with cover allowance)
0.5104"
Use this value when laying out your full cover spread.
Inches
0.5104"
Millimetres
12.96 mm
Pixels @ 300 DPI
153 px
Spine text is allowed
At 200 pages your spine is wide enough for a title and author name. Minimum text-safe spine width is 0.0625".
Amazon publishes one formula for every KDP book. The only variable is the paper-thickness multiplier. Here is the formula, followed by the exact arithmetic for a 100 page white paper paperback.
Formula
Spine Width = (Page Count x Paper Thickness) + 0.06" cover allowance
Worked example: 100 pages, white paper
Page count = 100
White paper thickness = 0.002252"
Pages contribution = 100 x 0.002252 = 0.2252"
Cover allowance = 0.0600"
Total spine width = 0.2252 + 0.0600 = 0.2852"
That is 7.24 mm, or 86 pixels at 300 DPI.
The 0.06" cover allowance accounts for the cover stock itself, which has its own thickness independent of the interior pages. Skipping this allowance is the most common reason a freshly designed spine fails KDP review.
All five paper-thickness constants Amazon publishes for KDP. Pick the one that matches your interior selection in the KDP dashboard.
| Paper type | Inches per page | Notes |
|---|---|---|
| White paper (paperback) | 0.002252" | Most common |
| Cream paper (paperback) | 0.0025" | Slightly thicker |
| Premium Color (paperback) | 0.002252" | 60# bright white |
| Standard Color (paperback) | 0.0032" | Thickest option |
| Hardcover Case Laminate | 0.002347" | 75 to 550 pages |
Cream paper is roughly 11 percent thicker than white. A 400 page book is 0.099" wider on cream than on white. Always recalculate if you change paper type after your cover is designed.
Every spine width KDP will accept, at every common page count, across all five paper types. Values include the 0.06" cover allowance.
| Pages | White (paperback) | Cream (paperback) | Premium Color | Standard Color | Hardcover Case Laminate |
|---|---|---|---|---|---|
| 24No spine text | 0.1140" | 0.1200" | 0.1140" | 0.1368" | n/a |
| 50No spine text | 0.1726" | 0.1850" | 0.1726" | 0.2200" | n/a |
| 75No spine text | 0.2289" | 0.2475" | 0.2289" | 0.3000" | 0.2360" |
| 100 | 0.2852" | 0.3100" | 0.2852" | 0.3800" | 0.2947" |
| 150 | 0.3978" | 0.4350" | 0.3978" | 0.5400" | 0.4121" |
| 200 | 0.5104" | 0.5600" | 0.5104" | 0.7000" | 0.5294" |
| 300 | 0.7356" | 0.8100" | 0.7356" | 1.0200" | 0.7641" |
| 400 | 0.9608" | 1.0600" | 0.9608" | 1.3400" | 0.9988" |
| 500 | 1.1860" | 1.3100" | 1.1860" | 1.6600" | 1.2335" |
| 600 | 1.4112" | 1.5600" | 1.4112" | 1.9800" | n/a |
| 700 | 1.6364" | 1.8100" | 1.6364" | 2.3000" | n/a |
| 828 | 1.9247" | 2.1300" | 1.9247" | 2.7096" | n/a |
Hardcover case laminate is limited to 75 to 550 pages on KDP. All other paper types support 24 to 828 pages. Books below 79 pages cannot have spine text under Amazon rules.
Amazon KDP will reject any cover that places text on the spine if your book has fewer than 79 pages. This is a hard rule, not a guideline. The minimum spine width that can carry text is 0.0625 inches, which roughly corresponds to 28 pages on white paper, but Amazon enforces the page-count rule first.
For books under 79 pages, your spine still exists in the cover file. Design it with continuous art or a solid colour. No title, no author name, no subtitle. The moment any character lands on the spine, Amazon's automated cover review will flag the file.
Paperback and hardcover use different paper-thickness multipliers. The cover allowance is the same 0.06", but hardcover books also wrap around the boards, so the total cover spread is wider. The spine width itself is just a paper calculation.
Paperback (white)
0.002252" per page
300 pages = 0.7356" spine.
Allowed page range: 24 to 828. Perfect-bound, no wrap. The spine is the only edge connecting front and back cover.
Hardcover (case laminate)
0.002347" per page
300 pages = 0.7641" spine.
Allowed page range: 75 to 550. Add 0.625" wrap on every side of the total cover canvas for the board overhang.
If you publish the same manuscript as both formats, you need two different cover files. The paperback and hardcover spines differ slightly because the paper multiplier differs, and the total cover dimensions differ because of the hardcover wrap. Use the cover size calculator for the full cover spread.
The spine sits between the front and back cover. Total cover width = (Trim Width x 2) + Spine Width + (Bleed x 2). Use the cover size calculator to get the full canvas in one step.
Add two vertical guides to mark the spine boundaries. In Photoshop or Affinity, position them at Bleed + Trim Width from the left, and Bleed + Trim Width + Spine Width from the left. Anything between those guides is the spine zone. Keep spine text 0.0625" inside each spine edge for safety.
The AI book cover generator auto-sizes your spine from your page count and paper choice, places the title and author at the safe-text margin, and exports a print-ready PDF with bleed baked in. No design software, no manual measurements.
Feed your page count and paper type straight into KDPEasy. The AI generates a print-ready front, back, and spine sized to your exact spec in roughly 2 minutes.
The KDP spine width formula is: Spine Width = (Page Count x Paper Thickness) + 0.06" cover allowance. Paper thickness depends on your paper type. White paper uses 0.002252 inches per page, cream uses 0.0025, premium color uses 0.002252, standard color uses 0.0032, and hardcover case laminate uses 0.002347. For a 200 page white paper paperback, that gives (200 x 0.002252) + 0.06 = 0.5104 inches.
0.002252 inches is the exact thickness of one page of KDP white paper. It is the multiplier Amazon uses in its official spine width formula for both white paper paperbacks and premium color paperbacks. Multiply your page count by 0.002252 to get the spine width contribution from the pages, then add 0.06" for the cover material to get the total spine width.
Take your page count and multiply by 0.002252. Then add 0.06 inches for the cover allowance. A 100 page book on white paper is (100 x 0.002252) + 0.06 = 0.2852 inches. A 300 page white paper book is (300 x 0.002252) + 0.06 = 0.7356 inches. The calculator above does this instantly and also gives you mm and 300 DPI pixel values.
A 200 page book on white paper has a spine width of 0.5104 inches (12.96 mm, 153 px at 300 DPI). On cream paper it is 0.56 inches. On standard color paper it is 0.7 inches. On hardcover case laminate it is 0.5294 inches. These all include the 0.06" cover allowance. Use the calculator above to switch paper types instantly.
No. Amazon KDP requires a minimum page count of 79 pages before you can place text on the spine. Books under 79 pages will have their spine text rejected during cover review. This is sometimes called the 79-page rule. If your book is below this threshold, design the spine with art only and move your title and author name to the front and back covers.
KDP hardcover case laminate uses 0.002347 inches per page. The formula is the same: Spine Width = (Page Count x 0.002347) + 0.06". A 300 page hardcover gives (300 x 0.002347) + 0.06 = 0.7641 inches. Note that hardcover books are limited to 75 to 550 pages on KDP and the total cover dimensions also include a 0.625" wrap allowance, which the cover size calculator handles separately.
Cream paper uses 0.0025 inches per page. The formula is Spine Width = (Page Count x 0.0025) + 0.06". A 200 page cream paper book is (200 x 0.0025) + 0.06 = 0.56 inches. Cream paper is roughly 11 percent thicker than white per page, so the same manuscript prints a noticeably fatter book on cream. Always recalculate the spine if you switch paper types after your cover is designed.
The 0.002252 value is the measured caliper thickness of the 60# white uncoated paper Amazon uses for KDP paperback interiors. It is a precise specification from Amazons print partner, not an approximation. Using 0.0025 or rounding to 0.0023 will produce a spine width that does not match the printed book, leading to spine creep, off-centre art, or a rejected cover at upload.
A 100 page white paper paperback has a spine width of (100 x 0.002252) + 0.06 = 0.2852 inches, or roughly 7.24 mm. A 100 page cream paper book is 0.31 inches. Both are wide enough for spine text under KDP rules since 100 pages exceeds the 79-page minimum and the spine is comfortably above the 0.0625" text-safe threshold.
No. The KDP spine width formula is exact. Adding extra width will misalign your front and back cover, causing the spine art to wrap onto the covers. If you want safety, keep spine text 0.0625" inside each spine edge so minor printing tolerance does not crop your title. The formula already includes a 0.06" cover allowance that handles the cover material itself.
AI-powered, print-ready front, back, and spine. Sized to your exact spec.