What DPI Should Interior Book Images Be for Print-on-Demand?

Interior book images should be 300 DPI (dots per inch) at the size they will print. That is the interior image DPI target every major print-on-demand platform requires or strongly recommends. Fall below it and your printed photographs, illustrations, and diagrams look soft or pixelated. Go far above it and you only bloat the file with no visible gain.

Knowing what DPI measures, how to check it, and what goes wrong will spare you costly reprints and production delays.

What Is the Difference Between DPI and PPI?

Authors meet both terms, DPI and PPI, and the industry uses them almost interchangeably. Strictly, DPI (dots per inch) is the density of physical ink dots a printer lays on paper. PPI (pixels per inch) is the density of pixels in a digital file. When a platform says “submit images at 300 DPI,” it wants a source file at 300 PPI at its intended print size. The printer then reproduces the image at the matching dot density.

For manuscript preparation the distinction rarely matters in practice. What matters is simple: the number in the image’s properties reads 300, DPI or PPI, at the size it will print. If your editor shows 72 PPI, the web default, the image is not print-ready. Sharpness on screen proves nothing.

The most useful habit is to think about resolution and print size together. A figure at 300 PPI postage-stamp size drops to 75 PPI once stretched across half a page.

Why Is 300 DPI the Universal Standard?

The 300 DPI standard exists because of how human vision works at reading distance. At reading distance, roughly 10–14 inches, the eye resolves detail down to about 300 dots per inch. Below that, printed images look grainy; above it, the eye perceives no improvement.

Lulu has publicly tested print quality at multiple resolutions and settled on 300 PPI as optimal. Its guidance notes that images above 600 PPI show negligible gain while inflating file size. Amazon KDP sets no maximum DPI but warns that excessively high resolutions can cause processing issues.

In practice, the sensible ceiling depends on what the image contains. Photographs and other continuous-tone images gain nothing above 300 DPI. Images that carry small text, such as charts and infographics, stay sharper at 400 DPI. Pure black-and-white line art (maps, pen drawings, fine-stroke diagrams) is the exception. Hard edges show jaggedness far more readily than a photo does, so line art benefits from 600 to 1200 DPI.

Past those thresholds, more is not better. Oversized files cause upload and preflight headaches without improving the printed page. A 300-page illustrated book saved with every image at 600 PPI can easily double the size of the exported PDF. No reader ever sees the difference, and the extra weight is exactly what stalls uploads and trips processing limits.

What Are the Platform-Specific Requirements?

While 300 DPI is the universal target, each platform enforces interior image DPI for print-on-demand a little differently:

The standout row is IngramSpark’s, per its File Creation Guide: for color interiors, 72 PPI is a hard automated gate. A single low-resolution image in a color interior stops the whole file at preflight. Blurb’s image requirements for BookWright add a ceiling that is easy to overlook: BookWright will not import an image above 75 megapixels, a limit of that software rather than of Blurb as a whole. A very large scanned illustration can exceed it. The same page sets 250 to 300 DPI at container size for books; the lower 90 DPI floor also on Blurb’s list belongs to wall art, not to book interiors. Publishing the same interior to more than one platform? Prepare to the strictest requirement so one file clears everywhere. That means 300 PPI, with no image under 72 PPI or over 75 megapixels.

What Happens When DPI Is Too Low?

Low DPI produces a set of specific, recognizable defects in a printed book:

• Photographs look pixelated, with visible squares of color instead of smooth gradation.
• Lines and curves develop jagged, staircase edges.
• Fine detail in illustrations vanishes.
• Text baked into images (captions, chart labels, infographic copy) turns blurry or illegible.

Web-optimized imagery is the classic culprit. Web images are typically saved at 72 PPI, whether they come from websites, social media, or stock libraries. That is fine for screens and useless for print: a photo that looks crisp on your monitor prints at roughly a quarter of the detail a press needs. The trap is that none of this shows on screen, where a 72 PPI image can look perfect. The shortfall only appears once the press renders it at physical size.

These defects are irreversible once the book is printed. The fix is a corrected file and a fresh upload, so it pays to catch resolution problems before submission. The same low-resolution source, incidentally, causes the blurry images authors see in Kindle ebooks. Fixing your originals improves both editions at once.

How Do You Check DPI, and Can You Fix a Low-Resolution Image?

Before submitting a print-on-demand file, verify that every interior image meets 300 DPI at its intended print size. The calculation is simple: required pixels = print width in inches × DPI. A 4-inch-wide image at 300 DPI needs to be at least 1,200 pixels wide. A full-page image on a 6″ × 9″ trim needs at least 1,500 pixels across. (Margins leave roughly 5 inches of printable width.)

Any mainstream image tool can show you the figures:

• In Adobe Photoshop, open Image → Image Size with “Resample” unchecked. The resolution field then shows the true figure at the image’s physical print dimensions.
• In free tools such as GIMP or IrfanView, the same figures appear in the image properties dialog.
• On a Mac, open the image in Preview and choose Tools → Adjust Size. Pixel dimensions and resolution appear together.

Whichever tool you use, check resolution at the image’s placed size in the layout, not at its raw pixel dimensions. The two only match when the image fills exactly the space its pixel count supports at 300 PPI. For a book with many figures, it is worth listing each image’s placed width and required pixel count. That quick checklist stops a single undersized figure slipping through to preflight and stalling the whole upload.

If checking reveals a shortfall, one warning matters above the rest: upsampling does not work. Artificially raising DPI, turning a 72 PPI image into 300 PPI with resampling on, adds no real detail. It stretches existing pixels into soft, interpolated mush that still prints poorly. If your source is 72 PPI, you need a higher-resolution original, not a resampled copy. No software can invent detail that was never captured in the first place. When you cannot find a better original, recreate the chart or diagram from scratch at full resolution. That is almost always faster than trying to rescue the low-resolution version.

How Should You Prepare Interior Images for Print-on-Demand?

Start with the highest-resolution source files you can get. If you are commissioning illustrations or shooting photographs, capture them well above 300 DPI at the intended print size. That leaves room to crop and adjust without dropping below the threshold.

Export the final manuscript as a PDF. PDF is the preferred submission format for every major platform because it preserves resolution, layout, and color on export. Avoid submitting Word files directly when the book contains images. Word can silently compress your images and quietly undo your resolution work.

Treat line art at the higher densities described earlier. Drawings, maps, and pen illustrations need 600 to 1200 DPI to keep thin lines crisp and free of stair-stepping.

Mind color space as well as resolution. Convert images to grayscale for black-and-white interiors. For color, the general rule is CMYK for anything headed to paper and RGB for anything headed to screen, but platforms differ in what they accept. IngramSpark expects CMYK, and Lulu recommends sRGB. KDP accepts RGB images and converts them to CMYK itself, though it advises against mixing color spaces in one file.

Finally, target 400 DPI rather than 300 for any image carrying embedded text, such as charts, diagrams, or annotated photos. The extra density keeps the small type sharp. This is the same reasoning behind avoiding blurry text inside images at print size.

Interior image DPI is one of the few print-on-demand rules with a single, universal answer. Aim for 300 DPI at print size, checked image by image before upload. Get the originals right, verify each image at its placed size, and export to PDF. The resolution warnings that preflight systems exist to catch simply never appear.

Frequently Asked Questions

Is 300 DPI enough for a full-page photo in my book?

Yes, provided the image is 300 PPI at the full print size, not at a smaller size then enlarged. For a full-page photo on a 6″ × 9″ trim, that means roughly 1,500 pixels across the printable width and 2,550 down its height. Check the resolution at the final placed dimensions. An image that is 300 PPI at 3 inches wide falls far below it once stretched to fill the page.

Can I increase a low-resolution image to 300 DPI in Photoshop?

Not usefully. Resampling to raise the DPI stretches the existing pixels and interpolates new ones. The result is soft and artificial, and it still prints poorly. Real resolution has to come from a higher-quality original or a freshly created file. Upsampling only changes the number, not the actual detail.

Do ebook images need to be 300 DPI too?

No. Ebook images are displayed on screens, so resolution is measured in total pixels rather than DPI. Equivalents of 72–150 DPI are usually fine. The 300 DPI rule applies to print interiors. If you publish both editions, prepare high-resolution originals for print and let the ebook conversion downscale from them.

What DPI should charts and text-based graphics be?

Target 400 DPI for any image that contains small text, such as charts, graphs, tables, or annotated diagrams. The higher density keeps thin strokes and small type crisp where 300 DPI can leave fine lettering slightly soft. Better still, where possible set such text as live text in the layout rather than baking it into an image.

Why did my book get rejected for low-resolution images?

Because at least one interior image fell below the platform’s floor at its placed size. IngramSpark, for example, rejects color interior files containing any image under 72 PPI. Preflight checks on other platforms hold or flag files when they detect low resolution. The fix is to replace the offending image with a version of at least 300 PPI at print size. Then re-export the PDF and resubmit.