gimp - print - fit whole page

I use gimp an an all-purpose image viewing/editing/printing software (which it was not designed for). Now I have a picture and want to upscale it and print it in the largest possible size on an A4 sheet of paper with the best possible interpolation method. And all this has to be simple enough to repeat thousands of time throughout my life. How?

Solution 1:

Astoundingly, GIMP does not seem to have an option for fitting the print to the page size. The only way I can see is to use Image → Print Size…. and set the print width or height parameters to dimensions suitable for printing on A4.

The size of the A4 page are 210 × 297 millimeters or 8.27 × 11.69 inches. The print should be a bit smaller to leave some margins. Change the larger axe and let the other adapt itself.

See the documentation for more details.

Solution 2:

It's easy:

1. File -> Print.
2. Switch to tab "Image Settings"
3. Change "Size width|height" with arrow buttons
4. See "preview" on the right.
5. Press "Print" button in the bottom.

Screenshot of a File -> Print window, where You can set image print size in Gimp before printing:

p.s. I have Gimp v 2.10.18. (now is 2021)
p.s.2 This setting will be resetted after closing print dialog window. If you need settings to be saved, use "Image" -> "Print size" as answered in the answer by @harrymc