Convert between millimetres and pixels at a given dpi
One inch is 25.4 millimetres. Pixels needed = finished size in mm / 25.4 x dpi. Printable size in mm = pixels x 25.4 / dpi.
A4 is 210mm by 297mm. 210 / 25.4 x 350 is about 2894 pixels, and 297 / 25.4 x 350 is about 4093 pixels. The first mode of this tool gives both.
It is the dpi you actually get when an image you already have is printed at the size you want. Divide the pixel count by the finished size in mm divided by 25.4. If the value is low, the print is enlarged and looks coarse.
Strictly, dpi is the density of dots a printer lays down and ppi is the density of pixels in the image data. In everyday prepress work both mean "how many per inch", and this calculation treats them the same.
About 2894 by 4093 pixels, from 210mm / 25.4 x 350 and 297mm / 25.4 x 350.
25.4 millimetres. Every dpi calculation here is based on that value.
Divide the pixel count by the finished size in mm divided by 25.4. A 3000px image printed 210mm wide gives 3000 / (210 / 25.4), about 363 dpi.
No. All calculation runs in your browser. Your input is never sent to or stored on a server.