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DPI

Printing & file preparation

Also called: dots per inch, resolution, PPI

How many dots of ink per inch an image contains at its printed size. KDP expects 300 DPI for print interiors and covers; screen images at 72 DPI print visibly soft.

DPI is not a property of an image on its own — it is the relationship between an image's pixel dimensions and the physical size it is printed at. A 1800 × 2700 pixel image is 300 DPI when printed at 6 × 9 inches and 150 DPI when stretched to 12 × 18.

Print needs roughly 300 DPI because ink on paper has no backlight and no subpixel trickery to hide softness. Images pulled from a website are typically 72 DPI at their display size, which is why a graphic that looks crisp on screen can print blurry: it has about a quarter of the pixels per inch that printing wants.

The practical rule is to work backwards. Decide the printed size in inches, multiply by 300, and that is the minimum pixel dimension your source image needs. Enlarging a smaller image to hit that number adds pixels without adding detail and does not help.

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Related terms

  • Full-wrap cover

    A single file containing back cover, spine, and front cover as one continuous image. It is the format KDP requires for print books, as opposed to a front-cover-only image.

  • Bleed

    Extra artwork extended past the trim line so that ink still reaches the edge of the finished book after cutting. KDP's bleed is 0.125 inches — on every outer edge of a cover, but on only three edges of an interior page.

  • PDF/X-1a

    A restricted PDF standard for print production: all fonts embedded, all colour in CMYK or spot, no transparency or scripting. It is the safest format to hand a print-on-demand service.

  • Trim size

    The finished width and height of a printed book after the pages are cut. KDP publishes a catalog of standard trim sizes, and the one you pick affects both layout and printing cost.