Is there a difference between the actual ruler and InDesign's inches scale?


I am pretty new to InDesign. I have set my scale to measure in inches. Today I had an actual physical-ruler (like the one image below) lying around so I picked it up and compared it with the scale on screen in InDesign.

enter image description here

To my surprise, I found a difference. Note that there are 16 points/stops that makes an inch. On comparison, I found the on-screen-scale to be one point shorter than an actual physical-ruler. I assume it is not supposed to be like this, what am I missing ? I have my document size view set to actual (Ctrl + 1).

UPDATE - Seems like I was missing the obvious concept, that the measurement in a software is just a simulation and are dependent on the resolution of the device they are used in.

I also got some very useful insights in this Photoshop article on View Print Size. Unlike InDesign, Photoshop has a menu named "Print Size" that can be used to get an almost accurate (It worked for me) size simulation provided you have a similar setting (again depends on your screen size and resolution).

Preference > Units&Rulers > New-doc-presolutions > ScreenRes. > 100 pixels/inch

1/27/2015 10:14:00 AM

Accepted Answer

Simply put the computer has no idea how big your screen is. 100% zoom does not really mean anything meaningful*. You can tell the computer how big your monitor actually is but this is a bit unreliable and has some side effects in other software.

So simply the computer is showing how big the relative ruler is. There is also no guarantee that the printer is calibrated correctly.There's also no guarantees that the pipeline is respecting your scaling settings. So you should measure your print. Nothing exactly new.

*Unless you make pixel based graphics for screens. Still no measure what it looks like on another screen. Pixel based things have NO inherent size in inches.

TL;DR What you see on screen does not need to reflect physical size, its still correct in relative terms.

1/27/2015 8:12:00 AM