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stylish_maker6609
Participant
August 28, 2025
Answered

Resizing images: 72ppi to 300ppi

  • August 28, 2025
  • 2 replies
  • 703 views

I use Photoshop frequently, but I need a refresher on resizing images. Many cameras take photos at 72ppi and the size in inches is huge. 

I need to provide images to someone with a  "miminum 300dpi", and it occured to me I'm just winging it when I resize images. I recognize ppi and dpi aren't the same, but they seem to get treated interchangeably.

The screenshot I included is a decent quality image, 36.667" x 27.472" at 72ppi. Is this image equivilant to a 4" x3" 300ppi image? How should I resize it?

 

I didn't have much luck finding a decent tutorial, maybe I'm just salty beause AI search results make everything difficult these days, ha ha. Can anyone point me to a good resource or give me the quick and dirty rundown?  

Correct answer davescm

Take the 'original' and change the resolution to 300 ppi without resampling. Save that as your master in PSD format. That gives you something easier to work with in InDesign.

For InDesign embed a link to that master and let InDesign handle resizing on the page. When you export a PDF you can choose to downsize any images over a certain ppi value in InDesign's export settings. If you feel the need to downsize first then use Resample and enter a smaller physical size. Save that as a downsized version and embed a link to that version. The disadvantage is that if you change the master you have to remember to change the downsized copy. Personally, I link to the master and keep the size down when exporting to PDF.

For screen use ppi is irrelevant, it is used to calculate a physical size when the image is printed. All that matters on screen is pixels. Check the required pixel size for the platform on which you intend to post, be that social media or a website, then use Image > Image Size with resample checked and enter the required pixel size. Then use Export or Export Save for Web to export a copy at the required size. Note that Save for Web will not include a ppi value (as it is irrelevant for screen use and will be ignored by browsers) and if you open it in Photoshop, Photoshop will add a default value of 72ppi.

Dave

2 replies

Conrad_C
Community Expert
Conrad_CCommunity Expert
Community Expert
August 28, 2025
quote

The screenshot I included is a decent quality image, 36.667" x 27.472" at 72ppi. Is this image equivilant to a 4" x3" 300ppi image? How should I resize it?

By @stylish_maker6609

 

It’s actually equivalent to 8.8 by 6.3 inches at 300 ppi.

The math works like this:

36.667 inches * 72 ppi = 2640 pixels wide

2640 px wide / 300 ppi = 8.8 inches wide

 

The demo below shows that Image Size does that math for you. Note that because we don’t want to change the total number of pixels in the image for this, I turn off Resample like davescm suggested, so that the image stays at 2640 x 1978 px both before and after changing the ppi Resolution:

 

 

You said you want 4" x 3" @ 300 ppi. If you set your image to 4 inches wide, then:

2640 px / 4 inches wide = 660 ppi.

But you want 300 ppi, so to maintain 4 inches wide while cutting the resolution from 660 to 300 ppi, some pixels will have to be thrown out. This is when you enable the Resample option, as shown in the demo below:

 

 

As you can see, after dropping it form 660 ppi to 300 ppi at 4 inches wide, the image had to go from 2640 px wide to 1200 px wide (4 inches * 300 ppi = 1200 pixels).

 

 

    S
    stylish_maker6609Author
    Participant
    August 28, 2025

    Thank you both, incredibly helpful!

    Any chance you can give me tips for routinely resizing large images for various uses, assuming I do need to resample in this case?

    This screenshot is a nice high quality image, but unwieldy for use in InDesign, especially for email sized PDFs. Say I want to keep the original, plus create a print quality version and a screen quality version - three images total. What would your "standard" parameters be? 

     

     

      davescm
      Community Expert
      davescmCommunity ExpertCorrect answer
      Community Expert
      August 28, 2025

      Take the 'original' and change the resolution to 300 ppi without resampling. Save that as your master in PSD format. That gives you something easier to work with in InDesign.

      For InDesign embed a link to that master and let InDesign handle resizing on the page. When you export a PDF you can choose to downsize any images over a certain ppi value in InDesign's export settings. If you feel the need to downsize first then use Resample and enter a smaller physical size. Save that as a downsized version and embed a link to that version. The disadvantage is that if you change the master you have to remember to change the downsized copy. Personally, I link to the master and keep the size down when exporting to PDF.

      For screen use ppi is irrelevant, it is used to calculate a physical size when the image is printed. All that matters on screen is pixels. Check the required pixel size for the platform on which you intend to post, be that social media or a website, then use Image > Image Size with resample checked and enter the required pixel size. Then use Export or Export Save for Web to export a copy at the required size. Note that Save for Web will not include a ppi value (as it is irrelevant for screen use and will be ignored by browsers) and if you open it in Photoshop, Photoshop will add a default value of 72ppi.

      Dave

        davescm
        Community Expert
        davescmCommunity Expert
        Community Expert
        August 28, 2025

        Hi,

        You are correct to use ppi (pixels per inch). dpi (dots per inch) is used in printing and describes the dots that are printed on paper, in a pattern, to make up those image pixels. Stick to ppi.

        72 ppi could be set by the camera, but it is also the default value used by Photoshop when no ppi value is contained in the image metadata (data stored alongside the image).

         

        So to answer your question, go to menu Image > Image Size uncheck Resample and set the Resolution to whatever value you require. With resample unchecked, the image itself is not changed - it will have the same number of pixels and not a single pixel will be changed. Only the ppi value, stored with the image, will be changed which means that the rulers and reported image size in real world units, i.e inches or centimetres, will change based on the new resolution value.

        Dave

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