Home › KDP says your cover is not 300 DPI
This is almost always the same misunderstanding, and it is not your fault: the number written in the file and the number that matters are two different things. Once you see the difference, the fix takes a minute.
The short version. DPI stored in an image file is a label. It has no effect on how much detail the image contains. What decides whether your cover prints at 300 DPI is the pixel dimensions divided by the physical size in inches. If those pixels are not there, changing the label to “300” changes nothing.
An image file contains a grid of pixels — say 1800 × 2700. Separately, it carries a small piece of metadata saying what physical size those pixels are intended to be printed at. That metadata is the DPI figure your image editor shows you.
The two are only loosely connected. You can take the same 1800 × 2700 pixels and label them 72 DPI, 300 DPI or 1200 DPI without altering a single pixel. The file size does not change. The image does not change. Only the label changes.
The real resolution is arithmetic:
effective DPI = pixel width ÷ printed width in inches
So 1800 pixels across a 6-inch-wide cover is 300 DPI. The same 1800 pixels across a 12-inch-wide wrap is 150 DPI, no matter what the metadata says.
This is the step that traps people. Your editor offers to change the resolution to 300, so you do, and the file still fails.
What that operation does depends on one checkbox, usually called Resample:
Neither path creates information that was never captured. The only real fix is to produce the artwork at the right pixel dimensions in the first place.
A KDP paperback wrap is a single flat image containing back cover, spine and front cover, with bleed all the way round. Its physical size is:
Bleed is 0.125″ on each edge. Spine width is your page count multiplied by the paper’s thickness per page. Multiply the resulting inches by 300 and you have the pixel dimensions the file must actually be.
Our spine width calculator does this and prints the exact pixel figures, then hands you a blank template already at those dimensions with trim, bleed, the spine fold, the safe area and the 2″ × 1.2″ barcode zone marked. It is free and needs no account.
Anything designed for a screen starts at screen resolution. A 1200-pixel-wide design looks perfect on a monitor and is nowhere near enough for a 12-inch wrap. There is no recovery except redrawing at print size.
If the spine width was estimated rather than calculated, the whole canvas is the wrong width — so even correct-looking artwork lands at the wrong effective DPI once it is scaled to fit. This is the most common version among people who built the cover before finishing the interior.
The canvas can be 3600 pixels wide and still contain a logo or photograph that was dropped in at 400 pixels and stretched. The file passes a naive DPI check and still prints soft in exactly one place. Check each placed element at 100% zoom.
Some export paths downsample images to save file size, and some PDF presets do it by default. If your source is correct but the export is not, look for a “downsample images” or “compress” option in the export settings and turn it off.
If step 3 fails, no export setting will save it. The artwork has to be produced larger.
Worth knowing while you are here, because the two failures often arrive together: the spine width depends on your page count, so a cover that was the correct size last week is the wrong size after you add pages. Rebuild the cover whenever the interior changes, or use something that derives the spine from the live page count instead of a number you typed once.
That is what our cover designer does — the wrap dimensions and the spine follow the book, so the pixel dimensions are correct by construction and cannot drift.
Get a blank wrap template at the exact pixel dimensions, free.
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