When to use Resize Image in CM
Resize an image to a size in centimetres, such as 3.5 × 4.5 cm for a photo. Choose the DPI and the tool converts cm to pixels for you, and stores the DPI in the file.
The best image settings depend on where the picture will be used. Pixel dimensions describe width and height; file size describes bytes. Changing one does not guarantee a particular value for the other. Keep the original, compare the result at its intended size, and choose a format accepted by the destination.