KDP COVER CALCULATOR
Every number KDP checks,
before you upload.
Spine width, full wrap size, bleed, safe area, 300 dpi pixel dimensions — computed from your trim size and page count. No signup, no email.
The three formulas behind the calculator
The whole spec reduces to three lines of arithmetic. Everything else — bleed, safe area, barcode clearance — is a fixed constant.
pages × paper thicknesstrim W × 2 + spine + 0.25trim H + 0.25Paper thickness is the only number people get wrong, because it changes with the paper you select and it is not in the KDP dashboard anywhere obvious:
| Paper | Thickness per page | 300 pp. spine |
|---|---|---|
| Black & white, white paper | 0.002252 in | 0.676 in |
| Black & white, cream paper | 0.0025 in | 0.750 in |
| Standard color, white paper | 0.002252 in | 0.676 in |
| Premium color, white paper | 0.002347 in | 0.704 in |
Why the page count keeps changing your file
Spine width is linear in page count, so adding two pages to the interior moves the spine by 0.0045 in — enough that a file laid out at 300 pages fails a 302-page book. That is the single most common reason a cover gets rejected after a proof read. It is also why a wrap should be built as one parametric canvas — back, spine and front — instead of a flat image you redo from scratch.
Skip the arithmetic. Build the whole wrap.
CoverNice lays out back, spine and front on one canvas, recalculates when you change the page count, and exports a 300 dpi print PDF with bleed and safe-area guides.
Questions people actually ask
How do I calculate a KDP spine width?
Multiply the page count by the paper thickness. KDP uses 0.002252 in per page for black & white on white paper, 0.0025 in for cream paper, 0.002252 in for standard color and 0.002347 in for premium color. A 300-page black & white book on white paper is therefore 300 × 0.002252 = 0.676 in. Always confirm the final number in KDP’s own previewer before you upload.
What is the full wrap size for a 6 × 9 book?
The wrap is two full covers plus the spine plus 0.125 in of bleed on every edge: (6 + 6 + spine + 0.25) × (9 + 0.25). For a 300-page 6 × 9 black & white book the spine is 0.676 in, so the file is 12.926 × 9.25 in.
When can I put text on the spine?
KDP prints a spine at all, but recommends leaving the spine blank under roughly 100 pages, because below that the spine is too thin to hold legible text. Our tool warns you below 100 pages and refuses to lay out vertical spine type when the spine is under 0.16 in.
Does the page count include the cover?
No. Use the interior page count only — the number of pages in the print-ready interior PDF, which must be an even number. Front matter and blank pages at the end all count.
Why was my cover rejected for size?
Almost always one of four things: a front-cover-only file stretched over the wrap, a missing 0.125 in bleed, a spine computed with the wrong paper type, or a PDF exported at low DPI. The calculator below gives you all four numbers so the file matches the spec the first time.