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

What DPI should your interior book images be? The short answer: 300 DPI (dots per inch). Every major print-on-demand platform — Amazon KDP, IngramSpark, Lulu, Blurb, and BookBaby — requires or strongly recommends 300 DPI for interior images. Fall below that threshold, and your printed photographs, illustrations, and diagrams will look soft, pixelated, or outright blurry. Go too far above it, and you will bloat your file size for no visible benefit.

Understanding what DPI actually means, how to check it, and what happens when you get it wrong will save you from costly reprints and production delays.

DPI vs. PPI: What Is the Difference?

Authors frequently encounter both terms — DPI and PPI — and the publishing industry uses them almost interchangeably, which creates confusion. Strictly speaking, DPI (dots per inch) refers to the density of physical ink dots a printer lays down on paper. PPI (pixels per inch) refers to the density of pixels in a digital image file. When a print-on-demand platform says “submit images at 300 DPI,” they really mean your source file should be 300 PPI so the printer can reproduce it at the equivalent dot density.

For practical purposes, the distinction rarely matters when preparing your manuscript. What matters is that the number in your image file’s properties reads 300 (whether labeled DPI or PPI) at the physical size you intend to print it. If your image editor shows 72 PPI — the default for web graphics — that image is not print-ready.

Why 300 DPI Is the Universal Standard

The 300 DPI standard exists because of how human vision works at typical reading distances. At roughly 10–14 inches from the page — the distance most people hold a book — the human eye can resolve detail down to about 300 individual dots per inch. Below that density, printed images start to look grainy or soft. Above it, the eye cannot perceive any improvement.

Lulu has empirically tested print quality at multiple resolutions and confirmed 300 PPI as optimal. Images rendered above 600 PPI showed negligible quality improvement while significantly increasing file size. Amazon KDP has no set maximum DPI but warns that excessively high resolutions may cause processing issues. In practice, there is no reason to exceed 300 DPI for photographic content or 400 DPI for images containing small text (such as charts or infographics).

Platform-Specific Requirements

While 300 DPI is the universal target, each platform enforces it slightly differently.

Amazon KDP recommends a minimum of 300 DPI for all interior images with no set maximum, though very high-resolution files may trigger processing errors or slow uploads.

IngramSpark recommends 300 PPI and will automatically reject interior files containing images below 72 PPI during its automated ingestion process. This is a hard floor — your file will not make it through preflight if any image falls below it.

Lulu recommends 300 PPI and advises staying under 600 PPI, as any resolution beyond that threshold is functionally wasted.

Blurb accepts images between 90 and 300 DPI at the size of the image container, with a hard maximum of 75 megapixels per image. They explicitly state they cannot offer reprints or replacements for problems caused by low-resolution images.

BookBaby requires 300 DPI and their Design Preflight team will place orders on hold when low-resolution images are detected, causing production delays.

Draft2Digital recommends 72–150 DPI for ebook interiors, but the standard 300 DPI requirement applies when distributing print editions through their platform.

What Happens When DPI Is Too Low

Low DPI produces a set of specific, identifiable visual defects in printed books. Photographs appear pixelated — individual squares of color become visible instead of smooth gradations. Lines and curves develop jagged, staircase-like edges. Fine details in illustrations disappear entirely. Text rendered within images (captions, chart labels, infographic copy) becomes illegible or blurred.

The most common source of these problems is using web-optimized images. Images downloaded from websites, social media, or online image libraries are typically saved at 72 PPI — perfectly adequate for screen display but wholly inadequate for print. A photograph that looks crisp on your monitor will print at roughly one-quarter the detail density a press needs.

These defects are irreversible once the book is printed. You cannot fix a low-resolution print run after the fact, and most platforms will not offer reprints or refunds for quality issues caused by source file resolution.

How to Check and Calculate DPI

Before submitting your manuscript, you should verify every interior image meets the 300 DPI threshold at its intended print size. The calculation is straightforward: 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 (with margins, roughly 5 inches of printable width) needs at least 1,500 pixels across.

In Adobe Photoshop, open Image > Image Size and check the resolution field with “Resample” unchecked. This shows you the true resolution at the image’s physical print dimensions. In free tools like GIMP or IrfanView, the same information appears in the image properties dialog. On a Mac, you can right-click any image file, choose Get Info, and look under More Info for the DPI field.

One critical warning: upsampling does not work. Artificially increasing DPI in Photoshop or similar software — changing a 72 PPI image to 300 PPI with resampling turned on — does not add real detail. It merely stretches existing pixels and produces soft, interpolated results that will still look poor in print. If your source image is 72 PPI, you need a higher-resolution original, not a resampled copy.

Best Practices for Preparing Interior Images

Start with the highest resolution source files available. If you are commissioning illustrations or taking photographs for your book, capture them at well above 300 DPI at the intended print size — this gives you room to crop and adjust without dropping below the threshold.

Always export your final manuscript as a PDF. PDF is the preferred submission format for all major POD platforms because it preserves image resolution, formatting, and color information during export. Avoid submitting Word documents directly when your book contains images, as Word’s internal compression can silently reduce image quality.

Pay attention to color space as well as resolution. For black-and-white interiors, convert all images to grayscale. For color interiors, Lulu recommends sRGB while IngramSpark requires CMYK — check your specific platform’s guidelines.

Finally, if your images contain embedded text — charts, diagrams, annotated photographs — consider targeting 400 DPI rather than 300 DPI. The higher resolution helps ensure small text within the image remains sharp and legible in print.

The Bottom Line

Three hundred DPI is the number to remember. It is the minimum resolution that produces professional-quality printed images, it is the standard every major print-on-demand platform requires, and it is the threshold below which visible quality problems are guaranteed. Check every image in your manuscript before you upload, use the pixel calculation formula to verify dimensions, and never rely on upsampling to rescue a low-resolution file. Getting this right before you submit saves time, money, and the frustration of holding a printed book that does not look the way you intended.