KDP Cover Design That Sells: Thumbnail-First Rules
Design covers for the 90-pixel thumbnail shoppers actually see. Contrast, type hierarchy, genre signalling, trim-size maths and the mistakes that cost sales.
Almost every purchase decision starts with a thumbnail roughly the size of a postage stamp. A cover that only works at full size is a cover that does not work.
These are the constraints professional cover designers work inside — and the ones AI-generated art most often breaks.
The thumbnail test
Export your cover at 90 pixels wide and look at it beside the current page-one results for your keyword. If the title is unreadable or the image reads as noise, the design fails regardless of how good it looks at full resolution.
- Title readable at 90px: non-negotiable.
- One focal element, not three competing ones.
- Contrast ratio high enough to survive Amazon's white background.
- Distinct silhouette compared with the neighbouring results.
Type hierarchy in three levels
- 1Level one — the hook word or the title, largest by a clear margin.
- 2Level two — the qualifier that proves fit: age range, count, duration.
- 3Level three — author name, smallest unless you have a following.
Two typefaces maximum. Pair one high-contrast display face with one neutral sans for everything else.
Signal the genre before you express yourself
Shoppers scan for category conventions first. A cozy mystery with a thriller palette loses the sale before the description is read. Study the top twenty covers in your category, list the shared conventions, then differentiate inside them rather than against them.
Print specifications you cannot ignore
- 300 DPI minimum for the full wrap, including bleed.
- Spine width depends on page count and paper type — recalculate after any interior change.
- Keep text at least 0.25 inches from every trim edge.
- Spine text only for books above 100 pages; below that, leave it blank.
- Use the KDP cover template for your exact trim size rather than estimating.
Frequently asked questions
What resolution does a KDP paperback cover need?
300 DPI across the full wrap including bleed. Lower resolution files are commonly rejected or print soft.
Can I use AI-generated cover art on Amazon KDP?
Yes, provided you hold the rights to use the output and you disclose AI-generated content where KDP asks during publishing. Always review the image for artefacts and text errors first.
How do I calculate spine width?
Spine width is page count multiplied by the per-page thickness of your chosen paper stock. Recalculate whenever the interior page count changes.