I like the convenience of being able to crop jpg/png images with Preview, but I would also like to be able occasionally to restrict the aspect ratio of the cropped image. This is useful, for instance, if I want to prepare images for printing in 4x6 or 5x7, while avoiding any surprise cropping made by the photo lab.

I am hoping there is a quick and easy way to do this (i.e., without needing to invoke the behemoth of image editing for this elementary task). Are you aware of one?

  • Are you willing to install additional software, providing it isn't a behemoth?
    – Ashley
    Commented May 10, 2014 at 12:02
  • @Ashley Yes indeed. I'll gladly install anything provided it doesn't come with 9999 additional features, takes 10 seconds to start, and occupies 3GB on my drive.
    – Calaf
    Commented May 11, 2014 at 3:43

8 Answers 8


In Photos (not iPhoto) click Edit


then Crop


then Aspect, and finally Original


As of this writing (August 2016), there is no way to do this using Preview or any other stock program in El Capitan. Photos is nearly stock though, and it's easy enough using Photos.

  • 1
    What is this "nearly stock" Photo? Is it an app? Do you have a link to it (either on the web or an App store line?) A quick Google & App Store search isn't showing any obvious results, and I've never heard of this app…
    – M. Justin
    Commented Dec 26, 2021 at 4:50
  • @M.Justin MacOS always had some photo application installed along with the OS. The app used to be called iPhoto. At some point (not sure when) Apple abandoned (the by-then rather backward and unsalvageable) iPhoto. To avoid confusion, and since the new app was genuinely built from scratch, they named the new app Photo. It is this one that you would install today on BigSur, and perhaps on Monterey—I haven't moved yet.
    – Calaf
    Commented Dec 29, 2021 at 16:58
  • On my Catalina install, I have a "Photos" app by Apple, but no app named "Photo"
    – M. Justin
    Commented Dec 29, 2021 at 17:02
  • 2
    @M.Justin You're right. I was staring so intently at the prefix, I missed that Apple also switched from the singular (en.wikipedia.org/wiki/IPhoto) to the plural (en.wikipedia.org/wiki/Apple_Photos). Fixed.
    – Calaf
    Commented Dec 31, 2021 at 15:21
  • 1
    Thanks for the clarification, that makes sense. :-) I think the other thing that threw me off is calling it "nearly stock". If it's included with the OS, wouldn't it also be a stock application?
    – M. Justin
    Commented Dec 31, 2021 at 17:47

There is no way to do exactly what you are specifying in Preview.app without doing a bit of math.

Holding down the shift key while using the select tool will force the select box to retain itself in square dimensions, while holding down the option key will open the select box from the center of where you begin your selection, while holding down both shift and option keys will implement both these features simultaneously. After creating the size of the select box that you want, you can use command-K to crop. Using the Adjust Size function in the Tools menu retains the aspect ratio by default.

Not what you asked for, but when using the select tool, you will notice numbers at 2 of the corners of the select box, and if you're very good with math (i.e. know if the numbers showing are multiples of your desired aspect ratio) and have a steady hand, you can accomplish what you are asking for on the fly. Otherwise, you'll have to figure out those dimensions beforehand or one at a time, and manually try to match up the numbers. In the end and in all circumstances, in my experience, mathematics is simply inescapable.

photo crop PRO

You may want to demo using an application dedicated to exactly what you want to do (rather than seeking functionality that just isn't there from such a simple, although often very useful, application such as Preview.app), for example, photo crop PRO. I personally would not recommend using Mac App Store ;-), but it is also available from the Mac App Store.


Alternatively, for an application far more powerful than either Preview or photo crop Pro, I've discovered darktable, which

"is an open source photography workflow application and RAW developer. A virtual lighttable and darkroom for photographers. It manages your digital negatives in a database, lets you view them through a zoomable lighttable and enables you to develop raw images and enhance them."

darktable can be installed manually, but is also maintained as a port using MacPorts, if you prefer to use package management. I've included step by step instructions for installing MacPorts and darktable below.


Another extremely powerful alternative suggested in another response (I thank you Ecnerwal!) is using the GIMP. The GIMP can be installed manually, or built from source using MacPorts. I've included instructions below on how to install the GIMP using MacPorts. If you know Adobe Photoshop well, you may want to demo using GIMPshop, which very cleverly and conveniently reconstructs the look and feel of the GIMP to appear and behave nearly just like Photoshop... and its all for free.


If you're looking for a mature package management solution, for OS X I recommend MacPorts. MacPorts requires an appropriate version of xcode; xcode_5.1.1.dmg is the most recent version for Mavericks and Mountain Lion, and will require registering for free as an Apple Developer. Once registered and logged in, the link above for xcode will initiate the xcode download.

Get to know MacPorts

Install MacPorts

Enter these commands using /Applications/Utilities/Terminal.app

  curl -Ok https://distfiles.macports.org/MacPorts/MacPorts-2.2.1.tar.bz2

  tar xf MacPorts-2.2.1.tar.bz2

  cd MacPorts-2.2.1



  sudo make install     # *not war!*

  cd ..

  rm -rf Macports-*

  sudo /opt/local/bin/port -v selfupdate

add MacPorts to your $PATH:

  export PATH=/opt/local/bin:/opt/local/sbin:$PATH

install darktable

  sudo port -vsc install darktable

install the GIMP

  sudo port -vsc install gimp

search MacPorts for other free photo utilities

  port search photo

to completely uninstall MacPorts

If, for whatever reason, you need to remove MacPorts:

  sudo port -dfp uninstall --follow-dependencies installed

  sudo port -dfp uninstall all

  sudo rm -rf /opt/local  

  sudo rm -rf /Library/Tcl/macports*

Do it in iPhoto.

  • Open a file.
  • Choose Edit.
  • Choose Crop or type c
  • Check constrain box for Original, the second dimension
  • Crop and hit Enter.
  • Save.

I don't think "what you want" really exists - so I'll answer with alternate ways to get there that are less painful than just staying in Preview.

I have a regular flow with fixed aspect where I use a tool from a camera suite (probably obsolete - certainly dubious about talking to the camera anymore with updated systems) that does fixed crop, resize to fixed pixels, and export - then open in Preview and use its color adjust tools (which get where I want faster than things with more options, and well-enough for the job.) You may find something similar (crop-wise) in software for a camera you own.

If "the behemoth" (or lack thereof) is your main issue, GIMP does fixed aspect crop for an attractive price (free or what you choose to donate) and without (IMHO) being a behemoth. It's quietly become quite decent, though it started out laughably bad.


Draw a diagonal from one corner to the other. Then hit Cmd-A and move one of the corresponding corner handles on the line to mark your desired region. Hit crop and then delete the line again.

You might not consider this simpler than opening image editing software :) but it is quite fast nonetheless.

  • I'm not clear on what you're saying. 1- Cmd-A just marks all the image. How does that help? 2- "..then delete the line again." What line?
    – Calaf
    Commented Sep 17, 2015 at 17:42
  • @Calaf I think Chris2u means draw the diagonal line using Tools > Annotate > Line. Then cmd-a helps to make a selection starting at top left, and you can move the bottom right along the marked diagonal.
    – Ashley
    Commented Sep 17, 2015 at 19:56
  • I see. But this is just an approximation, no? More importantly, I'm not just trying to maintain the aspect ratio of the original image. I'm trying to crop a part of the image with the aspect ratio of either 4:6 or 5:7.
    – Calaf
    Commented Sep 18, 2015 at 21:20

I love how everyone is saying there is no way... There is always a way, given not the best.

  1. Figure the aspect ratio you want (eg. 16:9)
  2. Get the dimensions matching the aspect ratio (eg. 1920x1080)
  3. Adjust the size of image on the longer side (eg. 1920), keep scale proportionally
  4. Select the whole image (CMD + A)
  5. Resize the selection so the shorter size fits your dimension (eg. 1080)
  6. Crop your image to your liking, move the selection
  7. Crop image

I know this thread is old but you could always do it with an Automator script.. You don't have control of what is cropped though...


If I understand your question correctly you could just use the Adjust Size… option from the Tools menu, and if it's not selected already, set Fit into to Custom.

  • 1
    Selecting "Fit into" only resizes the image to fit into the size as the name suggests. How does this help crop an image to the correct size?
    – grg
    Commented Oct 31, 2013 at 16:19

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