At the lower right corner of the screen, there is a button labled “Use same aspect as pixels”. If one zooms to 100% and then clicks this button, the image will be sized correctly according to ones PPI settings of the picture (see also this discussion. I.e. if the picture has 1000x1000 pixels, and 100 PPI, then the image will be 1 inch x 1 inch.
However, if I enable this, Krita reports two different zoom levels: The percentage on the lower right of the picture is not the same as the percentage show inside the canvas. I think this is quite confusing, but I’m not sure if it constitutes a bug, or is intended behaviour.
Any guesses?