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Fun Seeker
Inspiring
August 11, 2021
Answered

Best dimension for reflowable epub

  • August 11, 2021
  • 5 replies
  • 6659 views

Hi,

 

I would like to create a reflowable epub document with a fair number of full-color images. There will be no print version or fixed epub version. With this in mind, what would be the best dimensions so that it's viewable on a wide range of devices, and should I save the images at 300ppi? Thanks so much for any help you can provide. 

 

Kind regards,

 

Mark

    Correct answer BobLevine

    Here’s my $0.02 for all of this.

     

    For reflowable epub set up the document at 8.5” x 11” and be done with it. There are far too many epub readers to sit and overanalyze it. Using those dimensions should allow the books app on Mac or iPad to show two pages side by side when viewed in landscape mode. Others may or may not work that way.

     

    Of course, if you want to make yourself nuts over, have at it.

    5 replies

    BobLevine
    Community Expert
    BobLevineCommunity ExpertCorrect answer
    Community Expert
    August 12, 2021

    Here’s my $0.02 for all of this.

     

    For reflowable epub set up the document at 8.5” x 11” and be done with it. There are far too many epub readers to sit and overanalyze it. Using those dimensions should allow the books app on Mac or iPad to show two pages side by side when viewed in landscape mode. Others may or may not work that way.

     

    Of course, if you want to make yourself nuts over, have at it.

      Derek Cross
      Community Expert
      Derek CrossCommunity Expert
      Community Expert
      August 12, 2021

      In a Reflowable ePub, there’s no page size as such, you can create in InDesign the page any size you want, the Reflowable ePub page will resize to the page size of the device or viewer app.

      F
      Fun SeekerAuthor
      Inspiring
      August 12, 2021

      Hi Derek, I understand this. But for the people who open epubs on their desktop computer you want to make sure the images look sharp. That's where I'm getting hung up.

       

      Mark

      F
      Fun SeekerAuthor
      Inspiring
      August 12, 2021

      But for the people who open epubs on their desktop computer you want to make sure the images look sharp.

       

      Then it’s just a matter of choosing the device with the largest pixel dimension you want to target.

       

      You could target the largest iPad which is 2048 x 2732, and any smaller device is going to downsample rather than upsample the images to fit the available screen space. So if your document setup is 2048 x 2732 pixels and the epub Resolution is set to 72ppi, a full bleed image will export to the same dimensions and get downsampled on a smaller device.

       

      Alternatively your set up could be 6.827 x 9.107 inches with an export to 300ppi and a full bleed image would also export as 2048 x 2732 pixels (6.827 x 300 = 2048.1)

       

       


      That’s great. I’ll set the dimensions to 2048 px x 2732 px and export the epub at 72ppi.

       

      Regarding the images, I assume it would be best to export the images from Photoshop with those same dimensions @17233509 ppi, but what would happen to the images if you saved the images in Photoshop @300 ppi and exported the epub @17233509 ppi?

       

      Thanks.

      a m e r i g o d
      a m e r i g o d
      Participant
      August 11, 2021
      In such a case as a Reflowabe EPUB Reader: High Resolution

      Landscape View Orientation-
      >1,536 px Width
      + @ 150 ppi
      >1,152 px Height

      Portrait View Orientation-
      >1,152 px Width
      + @ 150 ppi
      > 1,536 px Height

      This should fill out the screen quite nicely and have pretty much the best
      view in high definition of original images within the EPUB reader. 🆗
        F
        Fun SeekerAuthor
        Inspiring
        August 12, 2021

        Hi Amerigod,

         

        Thanks for your help.

         

        On my desktop monitor and cellphone, I don’t see any difference in quality between an image saved @ 300ppi vs @150ppi. I did notice a drop off in quality with the picture saved @ 72ppi. Is this about right?

         

        Thanks.

        J E L
        Community Expert
        J E LCommunity Expert
        Community Expert
        August 11, 2021

        @Fun Seeker Hi Mark, these are great questions and you'll no doubt get a lot of advice here with a variety of opinions. Here are my thoughts: Since reflowable epubs are exactly that, the size you start with in InDesign does matter but not so much so that you have to figure it out exactly. If there will never be a print version (never say never!) you could start a document as a 6x9-inch trade book size, or a standard US letter 8.5 x 11. The viewer has a device with portrait or horizontal options... which is best? You have to layout and anchor your images for the reflowable version, making sure they can extend to the maximum space on many types of reading devices. Remember, an epub can also be read on a full size monitor with a browser interface. Most people think of Kindle or Nook or smartphones for reading epubs. So, when considering images that you want to look beautiful, I'd make them as large as possible and let the epub resize them as called for based on the viewing device. You could go with 72 or 150 ppi but keep 300ppi images as the originals **just in case**. The final MB size of the document probably matters for portability so use an image compressor tool or Photoshop action that doesn't degrade the jpg files but keeps them as small as possible. Also, consider the aspect ratios of the images (i.e., Kindle recommends a ratio of 9:11) but ideally they should be at least 600 pixels wide and 800 high. I always tend to go larger to at least 1200 on the long side and for large screens, 1920. Hope this is helpful!

          F
          Fun SeekerAuthor
          Inspiring
          August 12, 2021

          Hi Jain,

           

          Thanks for your help. Despite their popularity, I can’t find much helpful information about epub formatting/preparation online. There are tons of articles, but none of them focus on the core issues.

           

          I know reflowable epubs are responsive like websites, but choosing a proper document size is still important. With no printed or audio versions planned, I suspect that most people will view the book either on a cellphone, reader, or desktop monitor. It will contain a lot of images. I guess you could almost call it a picture book.

           

          On a cellphone or reader, the epub will resize as necessary. Simple enough. But how large should the document be to be viewed on a large desktop monitor? Is 600px x 800px enough? I see a lot of online tutorials recommending letter or A4 for epubs. There are so many templates available it is difficult to pick which is best.

           

          Mark

          rob day
          Community Expert
          rob dayCommunity Expert
          Community Expert
          August 11, 2021

          If you choose to set the document up to a pixel dimension and leave the ruler units as pixels the output dimensions shown in the Transform panel will match if you set the ePub’s Conversion Settings Resolution to 72ppi. So this image has a width of 2048 pixels and a Resolution of 72ppi will export it with a matching pixel width of 2048:

           

           

          If I change my rulers to Inches I can multiply the inch width by the export Resolution to know what the image pixel dimensions will be in the ePub.

           

          So with the rulers set to inches the image is 28.444", and the output to 72ppi will be 2,048px. If the output Resolution is set to 300ppi the width in pixels will be 8,533 pixels (28.444 x 300 = 8533.2) :

           

            F
            Fun SeekerAuthor
            Inspiring
            August 12, 2021

            Hi Rob,

             

            Thanks for your help. I normally leave everything in pixels, so there shouldn’t be any problems.

             

            Mark

             

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