Photoshop resizing canvas by small decimals

[EMMA29886805ujd4]

Hi there, 

I am unfortunately having an issue across all of my Photoshop files where after typing in set dimensions for the canvas or a layer, they are resized to a slightly different number once unselected and reselected again. This number is usually around 0.1mm off of the intended size typed in. 

I am struggling to find a solution anywhere else online and this issue is causing great amounts of trouble in my work as I am now unable to provide work / submit work at the exact dimensions as required by a client. 

Adobe Photoshop 2025 26.4.1

macOS Sequoia 15.3.1

Thank you.

[davescm · Accepted solution]

The answer is simple. Photoshop works in pixels not physical dimensions. The canvas must be sized in whole pixels, there cannot be a fraction of a pixel. When you type in a physical size it is converted to pixels using the document resolution (ppi or ppcm) and the nearest whole pixel value is used. That is then converted back to the physical size and you see the small change that is displayed on your screen.

If you need that exact physical size then you will also need to use a resolution value that divides exactly into that physical size to give a pixel value in whole numbers.

Dave