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We are preparing an e-poster and a printed poster for poster presentation at a conference. The organizer define the dimension of the poster as follows (everything is prepared in .pptx format and then exported to .pdf):

  • poster size in pixel: 1536px x 1080px
  • poster size in cm: 54.2cm x 38.1cm

How is this not a contradiction? Both "sizes" have the same aspect ratio but the actual sizes differ. The px-size translates to roughly 40.64cm x 28.56cm which is significantly smaller. A quick google search revealed that indeed a lot of congress organizer (like here or here) request the exact same dimension as stated above and I really wonder why? Isn't this something which will definitely lead to different printed poster sizes or am I missing something?

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To convert from pixels to real world dimensions needs one more number: printing resolution.

Seems the conversion between the dimensions you read off is equivalent to "72 dpi", dots per inch. Your software seems to be set to 96 dpi instead. If you change the dpi setting of your graphics software to 72 dpi then the pixels/dimensions in cm will match.

I will say that a poster actually printed at this resolution will possibly look quite ugly. I'd build your poster at a higher resolution and downsample the digital version to comply. That's also a really really tiny poster, at least by standards in my field. Maybe these tiny posters are normal elsewhere though?

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  • Thanks! I was using the standard options in Powerpoint where the difference first occurred to me - so the organizer are calculating with a lower print quality, that is interesting. For the actual e-poster it doesn't matter anyway (except maybe file size) but for the printed version I was a bit baffled. Is 96 dpi kind of standard?
    – user190080
    Jul 29, 2021 at 15:56
  • It does fit nicely on a reasonably sized computer monitor. But, yes, a "real" old time poster was ~1 meter wide and 1.8 meters tall.
    – Jon Custer
    Jul 29, 2021 at 15:59
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    @user190080 Yeah I'm not sure why that's the default in PowerPoint. That's a pretty low resolution for actual printing. Journals often request 300-600 dpi for paper figures, or even higher.
    – Bryan Krause ♦
    Jul 29, 2021 at 15:59
  • @JonCuster Yeah, the boards for the big conference in my field are 1.8 m wide and 1.2 m tall; most posters don't fill that entire space but are usually at least a meter wide; there is a common poster printer size that is 36", so that ends up being a common height.
    – Bryan Krause ♦
    Jul 29, 2021 at 16:02
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    @JonCuster Yeah, the airlines have gotten pickier about those tubes, too. They used to kind of just let them go and people would shove them in the overheads; now they're wanting to charge them as additional baggage. My advisor used to have a large format printer but only slightly large...so we had 11x19 pages to stack together which was only a very modest improvement over the 8.5x11s, but did at least fit into a smaller tube that would fit in a backpack height
    – Bryan Krause ♦
    Jul 29, 2021 at 16:55
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To add to @BryanKrause’s excellent answer, the conference organizers are being somewhat sloppy in using the unit size “pixel”, which has no standard physical size, when they probably mean “point” instead. A point in the printing world, when used as a unit, always measures exactly 1/72th of an inch as far as I’m aware.

As far as the discussion about printing resolution is concerned, you can print at whatever resolution suits your convenience (to the extent enabled by your hardware and software), as long as the physical poster dimensions are the required ones. So the issue of the printing quality doesn’t sound like a real concern here.

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  • Ah, that fits. They probably mixed it up (though apparently they aren’t then only once to fall for this error). Given points instead of pixel as the unit the size translates to the cm dimension.
    – user190080
    Jul 30, 2021 at 8:12

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