Unable to create image of a certain size (25mm x 11mm, 300DPI)

I’ve been asked to create an image of 25mm x 11mm, with 300 DPI. I’m far from an expert so I’ve simply tried to create a new image in GIMP with these specifications.

The program doesn’t allow me to use exactly 25mm x 11mm, the values are automatically adjusted (see screenshot).

create new image

I assume this is some constraint based on pixel to mm conversion or something like that.

What exactly causes this constraint and is there no way to create a image with the previously mentioned specifications?


  1. Because you are working with mm units, and the PPI uses imperial units.

  2. Because if you have exact mm you need to have halved pixels, which you can not, so the number is rounded to its nearest pixel count.

Let me do some math for you.

2.5 / 2.54 = 0.984 inch.

0.984 inch x 300 ppi = 295.275 px.

Source : Link , Question Author : Dolores The Third , Answer Author : Rafael

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