Look, I’ve been there. You upload your PDF, wait 24 hours, and get that annoying "Resize your cover" email.
Let’s fix that today. No robotic specs—just what actually works.
If Amazon keeps rejecting your cover, it’s usually one of three things:
you forgot the bleed, your spine calculation is slightly off, or you put text in the "danger zone".
The Golden Rule: Trim Size is NOT your file size.
Example: A 6x9 book is NOT a 6x9 PDF. It needs to be wider (for the spine) and taller (for the cutter).
1. Paperback Math (The Easy Part)
Paperbacks are flexible glued pages. The math is straightforward.
Don't guess the spine. If you are even 0.5mm off, the text will shift to the front cover.
Paper Type
Thickness per Page
100 Pages Example
White Paper (Standard)
0.002252"
0.225"
Cream Paper (Fiction)
0.0025"
0.250"
Color Paper (Premium)
0.002347"
0.234"
Rejection Alert: If your book is under 79 pages, do not put text on the spine.
KDP machines can't print on spines that thin, and they will block your book.
2. Hardcover Math (The Tricky Part)
This is where most creators fail. Hardcovers aren't just bigger paperbacks.
They wrap around a cardboard case. This means your image needs to be HUGE compared to the actual book.
The Wrap Factor: You need an extra 0.59 inches (15mm) on ALL four sides of your cover art.
This part gets folded behind the cover. Do not put any important text or logos here—they will disappear!
Even if your size is perfect, these layout mistakes will get you rejected:
The Barcode Box: Amazon automatically places a 2" x 1.2" yellow box on the bottom right of your back cover. If you put text or a logo there, it gets covered. Keep that corner empty!
The Safety Margin: Keep all text at least 0.375" (9.5mm) away from every edge. The cutting machines aren't perfect; if your text is too close, it gets chopped off.
Dark Covers: If you use a pitch-black background (#000000), it might print dark grey. Use "Rich Black" (C:60 M:40 Y:40 K:100) for a deep, professional look.
Hate doing math?
I built a tool that does this instantly. Just enter your page count and hit go.
It gives you the exact pixel and inch dimensions for Photoshop or Canva.
Screens use RGB (light), printers use CMYK (ink). Neon greens and bright blues often turn muddy in print. Always design in CMYK mode if possible, or expect a slight color shift.
Absolutely not. Hardcovers have a different aspect ratio because of the "wrap." If you just stretch it, your title will look weird or get cut off. You need to redesign the edges.
Even a small bleed mismatch can cause white lines after trimming. KDP’s system is strict because printing machines are not perfectly aligned. Always include full bleed, even if your design looks “safe”.
Yes. If you add or remove even one page after designing the cover, the spine width changes. Always finalize your interior PDF before calculating the cover size.
KDP’s error messages are generic. In most cases, the issue is either missing bleed, wrong spine width, or hardcover wrap margins not included. Their system checks math, not visuals.
Yes, but only if you use exact custom dimensions and export as PDF Print. Avoid dragging elements too close to edges, and never rely on Canva’s preset book sizes.
Spine centering shifts during binding. Always visually center text with extra margin tolerance. Thin spines exaggerate even tiny alignment errors.
PDF (Print Quality). Don't upload JPEGs or PNGs for the final cover; they often get pixelated. If using Canva, choose "PDF Print" and check "Crop Marks and Bleed" just to be safe (though KDP prefers no crop marks).