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One-Click KDP Preflight: Alhora Finds Under 300 DPI Images

September 9, 2026
One-Click KDP Preflight: Alhora Finds Under 300 DPI Images

Amazon KDP expects every image, cover or interior, to hit at least 300 DPI at its final printed size, and that last part is the detail most authors miss. Effective DPI, meaning the resolution the image actually delivers once it's placed at the size it prints, is what determines whether a photo looks sharp on the page or turns to mush. Push resolution too far past that (say, well beyond 600 DPI) and you risk slow processing instead of better quality. The checklist for verifying this yourself is a few sections down.

TL;DR:

  • Images should be at least 300 DPI at the final print size, with a practical upper limit around 600 DPI to avoid processing delays.
  • A 1200 pixel wide image placed at 4 inches in print produces 300 DPI, but stretching it larger reduces effective DPI and softness may appear.
  • Replacing low-resolution images with originals or carefully upscaling while checking at 100% prevents quality loss before uploading.
  • Automated tools like Alhora can flag images below 300 DPI during export, streamlining the preflight process.
  • Authors should verify effective DPI at the printed layout, flatten layers, strip metadata, and order proof copies to avoid resubmission issues.
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Table of Contents

KDP Image DPI Rules and Upload Limits, Explained

KDP's own guidance is narrower than most authors assume. It sets a floor, not a fixed target, and it cares more about consistency than perfection.

  • Minimum: 300 DPI for both cover and interior images, measured at final printed size.
  • No hard ceiling, but KDP warns that unnecessarily high resolution can slow down file processing or cause timeouts during upload.
  • Practical upper bound: most formatters treat a reasonable upper limit for DPI to balance print quality and file size, as excessively high DPI can lead to processing delays without noticeable improvements.
  • File handling: KDP's paperback submission guidelines call for flattening transparent objects and exporting optimized PDFs before upload, plus keeping overall file size within KDP's processing limits.

None of this is arbitrary. Amazon's automated checks flag low-resolution images mainly to protect the reading experience, since a blurry photo on page 40 generates the same one-star review as a typo on page one.

What DPI Actually Means for a Printed Page

DPI stands for dots per inch, and it only means something once you attach it to a physical size. A photo can be labeled "300 DPI" in its file metadata and still print blurry if it's stretched larger than its pixel count supports. Screens complicate this further: monitors typically display around 72 to 96 pixels per inch, so an image that looks crisp on your laptop can fall apart at print size.

The math is simple:

  1. Take the image's pixel width or height.
  2. Divide by the number of inches it will occupy on the printed page.
  3. The result is your effective DPI at that size.

A 1200 pixel wide image placed into a 4-inch wide space gives you 300 DPI (1200 ÷ 4 = 300). Shrink that same image into a 2-inch space and it jumps to 600 DPI, sharper than needed. Stretch it to 8 inches and it drops to 150 DPI, visibly soft in print.

One warning worth repeating: relabeling a file's metadata to say "300 DPI" does not add pixels. It just changes a number in the file header. The image still prints exactly as sharp, or as soft, as its actual pixel count allows.

Pixel grid beside unchanged image metadata

Cover and Interior DPI Targets With Real Pixel Sizes

Numbers make this easier to plan around than percentages ever will.

  • Front cover panel, 6×9 trim: a typical target pixel dimension is calculated to meet minimum 300 DPI for that print size. A full wrap cover requires more pixels to accommodate the spine and back-cover.
  • Marketing cover image: KDP recommends around 2,560 × 1,600 pixels at a 300 DPI minimum, with the marketing file kept at 5MB or less.
  • Full-page interior photos: aim for 300 DPI at the trim size you're printing, so a 6×9 full-bleed photo needs roughly the same 1,800 × 2,700 pixel target as the cover panel.
  • Small inline images (icons, diagrams, decorative dividers): 300 DPI still applies, but since the physical footprint is tiny, the pixel count required is much lower.
  • Line art, engravings, fine detail work: pushing toward 600 DPI genuinely helps here, since fine linework benefits from the extra resolution. Expect the file size to grow accordingly.

How to Calculate Effective DPI Before You Upload

Checking this yourself takes about two minutes per image, and it beats finding out from a rejection email.

  1. Open the image file's properties (right-click on Windows, "Get Info" on Mac) or check the pixel dimensions inside your image editor.
  2. Find the printed size you intend for that image, either from your book's trim size or from the layout frame it sits in.
  3. Divide pixel width by intended width in inches (or pixel height by height in inches). The lower of the two numbers is your effective DPI.

Worked example: your interior photo is 2,400 × 1,600 pixels, and you're placing it at 8 × 5.33 inches on a 6×9 trim page. 2,400 ÷ 8 = 300 DPI. 1,600 ÷ 5.33 = 300 DPI. That image clears the bar. Drop the same file into a 12 × 8 inch spread instead, and effective DPI falls to 200, below KDP's threshold. As one preflight guide focused on this exact issue puts it, dividing pixels by printed inches is the calculation that matters, not whatever number sits in the file's metadata.

Fixing Low-Resolution Images Without Wrecking Them

Once you've found a problem image, you have three real options, and they're not equally good.

  • Best fix: go back to the original source and grab a larger file, or repurchase a higher-resolution license if the image came from a stock site. Nothing beats native pixels.
  • Second option: use an upscaler carefully, then zoom in on the result at 100% and check for waxy skin tones, warped text, or smeared detail before trusting it.
  • Export correctly: flatten all layers, especially transparent ones, and export as a high-quality TIFF or PDF Print file rather than a compressed JPEG. Avoid running the file through a second round of compression after export, since that's a common way a technically adequate image ends up looking soft.

If it looks fine there but you still feel uneasy about it at 100%, trust the 100% view. That's closer to what the printed page will actually show.*

For readers formatting ebook interiors alongside print, the compression math works differently since screen display doesn't demand the same pixel density as paper. A guide to sizing images in EPUB files covers that trade-off in more depth.

A Publisher-Grade Preflight Routine Before You Upload

Professional formatters run the same sequence every time, regardless of how confident they feel about a given file.

  1. Check pixel dimensions on every image slated for print.
  2. Calculate effective DPI against the size it will actually occupy in the layout.
  3. Replace or upscale anything that falls under 300 DPI.
  4. Flatten transparency and remove stray metadata, crop marks, or invisible objects.
  5. Export as PDF Print, not a generic PDF setting.
  6. Inspect the exported file at 200% zoom, page by page, watching specifically for softness around image edges.
  7. Order a physical proof copy before hitting publish on the full print run.

Pro Tip: Zooming to 200% catches problems the on-screen preview hides completely. A photo can look acceptable at 100% and reveal visible softness the moment you double the zoom.

Some book formatting tools run a version of steps one through five during export, flagging any image below the 300 DPI threshold at its placed size before you reach KDP's upload screen. That doesn't replace the proof copy. It just means you order the proof for confirmation, not diagnosis.

Why Your Upload Got Flagged for Low Resolution

Most low-resolution warnings trace back to a small handful of repeat offenders.

  • Screenshots used as book images: these are inherently limited to screen resolution and almost never clear 300 DPI at any usable print size.
  • Stretched assets: an image that was fine at its original size, resized larger inside the layout without regard for pixel count.
  • Over-compressed exports: JPEG compression applied twice, once during editing and again during PDF export, degrading detail each time.
  • Layered transparency left unflattened, which can cause KDP's processor to misread the image entirely.

The fastest diagnosis method is KDP's own online previewer, paired with a physical proof. The previewer catches obvious flags; the proof catches the subtler softness that a screen, lit and small, tends to hide.

Your Last-Minute Checklist Before Hitting Publish

Run through this list before every upload, not just the first one.

  • Effective DPI confirmed at final placed size, not just at the image's native size.
  • Color mode set correctly (CMYK for most print interiors, RGB for ebook and marketing covers).
  • All layers flattened, transparency handled, and stray metadata stripped.
  • File exported as PDF Print with no extra compression pass applied afterward.
  • Total file size within KDP's processing limits.
  • Both the KDP previewer and a physical proof copy checked before final approval.

Those last two steps alone catch the majority of resubmissions authors deal with.

What I've Learned About DPI Mistakes Authors Actually Make

The DPI problems I see most often aren't complicated. They're AI-generated cover art pulled at screen resolution, phone screenshots dropped into interiors, or social media graphics that were never meant for print. A slightly soft inline icon rarely matters. A photo book with soft images matters enormously, and no amount of confidence in your export settings replaces actually ordering a proof. When in doubt, order the proof. It costs less than a stack of one-star reviews.

— James

How Alhora Turns DPI Checks Into a One-Click Step

Alhora replaces the manual pixel math with an automated check built into export. Instead of opening file properties on forty interior images one by one, Alhora's KDP formatting workflow flags anything under 300 DPI at its placed size, flattens transparency automatically, and exports a KDP-ready PDF Print file without a second compression pass sneaking in.

Alhora

That's the practical advantage over doing this by hand: you catch resolution problems during layout, not after a rejection email or a printed proof that arrives soft. Automated checks flag issues without touching your actual text or design choices, so you stay in control of every creative decision. Import your manuscript, run the export, and order your proof copy with confidence that the DPI math already checked out.

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