Image Upscaler for Print
Tell it the size you are printing at and it says whether your image has the pixels for 300 DPI — free, on your device, no account. If it is short, upscaling can reach it.
The diagnosis happens on this device — nothing is uploaded to work out whether your image has enough pixels. Upscaling is different: it runs on our servers, so pressing it uploads the image to your own library and spends credits.
DPI is not a property of your file
An image has pixels; a printed page has inches. Divide one by the other and you get DPI, which means the same file is 300 DPI on one cover and 150 on a larger one. That is why the number stamped inside a JPEG tells you almost nothing, and why this tool asks for the print size before it answers.
KDP’s own guidance asks for 300 DPI at the trim you are publishing at. The same formula runs here, in the Book Studio editor’s readout, and in the export preflight — so a verdict you get on this page is the verdict your book gets.
When not to upscale
Upscaling is the second-best fix and it is worth saying so. If you still have the original photograph, the render, or the vector, going back to it beats any model — those pixels are real. If the shortfall is small, printing at a slightly smaller size costs nothing. And past about four times, an upscaler stops recovering detail and starts inventing it, which is why this tool refuses rather than taking the credit.
Frequently asked questions
Why does the diagnosis need no account but the upscale does?
Because they cost different things. Working out whether your image has enough pixels is arithmetic — your browser does it, nothing is uploaded, and it is free forever. Adding pixels is a model running on a GPU, which costs real money each time, so it needs a free account and a credit. We would rather tell you the answer for nothing and charge only when there is work to do.
Does upscaling invent detail?
A little, and that is why there is a ceiling. Up to about four times the linear size, an upscaler is mostly recovering edges that the pixels already imply, and a cover printed from it looks right. Beyond that it is guessing, and guessed detail on a face or a piece of text looks worse than the soft original. So we refuse past ×4 and say so rather than selling you a disappointment.
Is my image uploaded?
The diagnosis, no — it happens entirely on your device. The upscale, yes, and it has to be: the model runs on our servers. Pressing the upscale button uploads the image to your own library, and nothing is sent before that press. This is the one image tool here that uploads, and the other three say so too, in the opposite direction.
What resolution do I actually need?
KDP asks for 300 DPI at the printed size, which is a claim about pixels and inches together, never about the file alone. A 1800×2700 image is 300 DPI on a 6×9 in cover and 150 DPI on a 12×18 in one — same file, different verdict. That is why this tool asks what size you are printing at before it answers.
What if the picture is already big enough?
Then it says so and offers nothing to buy. Some files carry a DPI label that disagrees with their pixels; if yours is only mislabelled, the free 300 DPI converter relabels it without changing an image that was already fine.
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