# How to get a 1:1 scale print preview?

this question is actually a bit special, so I didn't know exactly how to formulate it. What I actually want is to see an image on the screen at same size (or as much close as possible) to the size it will get once printed. In other words, a 1:1 scale preview. I will provide the numbers I'm working with.

• The target paper size is a DIN A4.
• The target DPI is 350.
• The image resolution is 3840 x 2160 pixels.
• The display has a native resolution of 1920 x 1080 (which is the actual resolution configured) and a diagonal size of 21.5 inches.
• Based on the display numbers above, and according to this site, the pixel density of the screen is 102 DPI.

Now, when I open the image on GIMP and change the zoom level to 100%, since the image is so much bigger than the screen resolution it doesn't fit on the screen, and it looks actually much bigger than the actual size it will get on the paper. So, the question is which zoom level do I need to set in order to see the image as much big as it will be on the paper, or as much close as possible, in order to get a more accurate preview.

With the numbers provided there should be some calculations that could be done to figure it out, but I just don't see how to make sense of these numbers. Maybe I should ask this on a Math related StackExchange site instead? I considered that, but since you graphic designers are more familiar with DPI and printing maybe you can help me out here.

Sorry if this wasn't the right place to ask this.

Could I suggest the "really, really obvious empirical method"?

Get a sheet of A4.
Hold it up to the screen.
Change the image zoom scale until it matches.

Forget DPI & pixel density. You just want it "the same apparent size".
Unless you have a screen with a physical pixel density of 350 & at least 3840x2160, you cannot achieve a complete 1:1 image on screen.
You can either see all the pixels or all the sheet & ne'er the twain shall meet.

• Ha ha! Yeah, I already thought about holding an A4 sheet on the screen and adjust the zoom, but I was just hoping there would be some better approach. Because that trick it's not possible if the target paper is an A3 because it wouldn't fit on the screen. Feb 3, 2019 at 10:34
• If all else remains the same, then so does your zoom value. Otherwise get it to fit A4 then double it. Feb 3, 2019 at 10:39
• Between A4 and A3 it's is not 2x but 1.4142x (sqrt(2)) Feb 3, 2019 at 22:52
• @xenoid - point taken. I simply meant double the dimensions; but you're right on the scale factor. Feb 4, 2019 at 8:50
1. Make sure that the screen definition as seen by Gimp is the real one: `Edit>Preferences>Interface>Display>Monitor resolution` (in 2.8: `Edit>Preferences>Display>Monitor resolution`). This part is the most often overlooked. If necessary, calibrate it(*).
2. Make sure that the print definition (ie, the DPI for the printer) is correct: `Image>Print size`
3. Untick `View>Dot for dot` (and of course set zoom to 100%).

(*) You can trust Gimp. A good test is to use one of the Letter/A4 templates. Create the blank image, untick `View>Dot-for-dot` and set zoom to 100%. Measure the width of the canvas with a "physical" ruler or compare with a sheet of printer paper. If you don't get 210mm for A4 or 8.5" for Letter, your screen definition as seen by Gimp is wrong.

• I don't see those options in the preferences menu. Which version are you using? I'm using 2.8.18 Also, I'm using Windows, maybe the preferences layout varies depending on the OS. Feb 3, 2019 at 13:48
• I already found the option. That did the trick. Thank you! Feb 3, 2019 at 18:23

It seems to me the zoom you want is 102/350% = 29%