Ruler tool actual real size in real life

[yasin24092399czz8]

Hi i always create a4 size canvas and I just noticed that when I use ruler tool to measure photo or want actual size of photo in real life to get print it's doesn't giving me the same correct size what I actually measured why ? And how to solve

[gener7]

This is done using the  View > Print Size command. You have to set it up first.

Go to Photoshop Preferences > Units & Rulers

There you enter your Screen Resolution in Pixels/Inch or Pixels/Centimeter

I use a ruler to find the physical horizontal screen size of my monitor:  11.25 inches in my case.

Then I find the the monitor Display Resolution setting in pixels: 1280 px Horizontal x 800 px Vertical from MacOS System Preferences:

So  1280/11.25 = 113.7  Since pixels are whole units, I round it to 114 ppi and enter it here:

Click OK, and your onscreen rulers (Cmd R) and A4 document should match a physical ruler when using View > Print Size.

[Conrad C · Accepted solution]

One step: Choose View > Actual Size.

This is a recently added command that is intended to make the rulers match print size, by correcting for the detected resolution of your display.

If Actual Size does not make the on-screen rulers match a real ruler, your operating system or graphics hardware may be older. In that case, the older View > Print Size command still works, but requires those extra steps to set up.

[davescm · Accepted solution]

"If Actual Size does not make the on-screen rulers match a real ruler, your operating system or graphics hardware may be older"

There can be a mismatch in current systems also. I use Windows 10 (v21H2), an NVidia RTX3090, and two Eizo CS2731 monitors connected via Dataport for 10 bit/channel working.

View > Actual size - slightly, but consistently, undersizes the rulers.

View > Print Size with Preferences >Units and Rulers >Screen Resolution set to 109 ppi is accurate

Dave

[gener7 · Accepted solution]

Yes, that does the trick on my 10 y.o. Mac.  So that will be Plan A. I'll keep the older instructions as Plan B.

Thanks for chipping in, Dave. I guess it all varies depending on configuration.