Preview with guides
What is checked
Six things printers reject covers for.
Size. The cover is one wide page: back, spine and front, plus 0.125 in (3.2 mm) of bleed on every side. The checker works out the size your book needs and compares it with your file, to within 0.4 mm — and if the width is off, it tells you which page count your spine was built for.
Resolution. Images need at least 300 dpi at the printed size. For an image cover the checker divides the pixels by the inches; in a PDF it measures every placed image at the size it is drawn.
Colour. Both printers print in CMYK. The checker reads the colour space of each image in a PDF (and of a JPG), and looks for the PDF/X marker IngramSpark asks for.
Safe zone and barcode. Drawn over your design: keep text 0.125 in inside the trim and the folds, spine text 0.0625 in from each fold, and leave a 2 × 1.2 in space for the barcode on the back unless you add your own.
Pages. KDP and IngramSpark both want the cover as a single-page PDF.
Spine text. KDP needs at least 80 pages for text on the spine; IngramSpark allows none below 48 pages.
Why the checker reads PDFs the way it does
The size check reads the PDF’s page boxes (MediaBox, TrimBox, BleedBox) and the colour spaces with a few lines of our own code, so it works even offline. To draw the preview and measure image resolution, the page loads pdf.js — the open-source PDF viewer built into Firefox — from cdnjs, only when you choose a PDF. Your file stays on your computer either way.
Common mistakes
- A cover built for an old page count. The interior changed, the spine didn’t. The checker shows the page count your file’s spine matches.
- No bleed. A cover exactly the size of the book leaves white slivers after cutting. Extend the background 0.125 in past every edge.
- A low-resolution image stretched to fit. A web image of 1,500 pixels across a 12-inch cover prints at 125 dpi: soft and blocky.
- Text too close to the edge or the folds. Cutting and folding can move by an eighth of an inch. Keep titles and author names inside the green lines.
- Uploading an image instead of a PDF. Both printers take the print cover as a PDF; export your design to PDF at the size above.
Sources, checked 20 October 2026: Amazon KDP — Create a Paperback Cover · IngramSpark — File Creation Guide (Cover requirements) · IngramSpark — Paper Specifications. IngramSpark covers are built on the template from its cover generator; the checker compares the trim area when your PDF marks it. This tool helps you catch problems early; the printer’s own review has the final word.
Questions
Covers, answered.
What size should my KDP paperback cover PDF be?
Back cover + spine + front cover, plus 0.125 in of bleed on every side. A 300-page 6 × 9 in book on white paper has a 0.6756 in spine, so the PDF is 12.9256 × 9.25 in. The cover must be a single PDF page.
What resolution does a book cover need?
At least 300 dpi at the printed size. For a 12.93 × 9.25 in cover that means about 3,878 × 2,775 pixels. IngramSpark says images under 200 ppi may be rejected.
Should my cover be RGB or CMYK?
Both KDP and IngramSpark print in CMYK. KDP recommends CMYK images and advises against mixing colour spaces; IngramSpark asks for CMYK and converts RGB files, which can shift colours.
What is the safe zone on a book cover?
The area where text is safe from trimming and from the spine folds: at least 0.125 in (3.2 mm) inside the trim lines and the folds. Spine text needs 0.0625 in (1.6 mm) from each fold. IngramSpark recommends 0.25 in for important text.
Is my cover uploaded when I use this checker?
No. The file is opened by your own browser and never leaves your computer. For PDFs, the page loads the open-source pdf.js viewer from cdnjs to draw the preview; only that code is downloaded, your file is not sent anywhere.
Tellurin calculates this for you and builds the full cover at the right size for KDP or IngramSpark — and checks it before export. About Tellurin