What DPI actually measures
DPI describes output hardware. A printer places dots of ink side by side, and a higher dot count packs more of them into each inch, which smooths gradients and sharpens fine lines.
The value is a printer or scanner setting rather than a property baked into a photograph. Image files carry pixel dimensions, and software combines those pixels with a DPI value when it sends the job to a device.
DPI, pixel count, and print size
Print size follows from a simple relationship: pixels divided by DPI gives inches. A 2,400-pixel-wide image placed at 300 DPI covers eight inches, and the same pixels at 150 DPI cover sixteen inches with lower density.
Publishers commonly aim for around 300 DPI for photographs in print and accept lower values for large output viewed from a distance, since the eye cannot resolve the extra dots that far back.
- Higher DPI means denser dots and finer detail on paper
- Print size equals pixel count divided by DPI
- Changing DPI does not alter the pixels in your file
- Screen display ignores printer DPI settings
DPI and digital files
For anything that stays on a screen, DPI has no effect. A web page uses the image's pixels directly, so only pixel dimensions and file size matter for loading and upload limits.
That is why resizing pixels is the meaningful edit online. Filekind resize tools adjust dimensions in the browser, which is what actually changes what a website or form receives.