Easy Ways to Resize an Image on a Mac (Without Buying Software)

PDF download Download Article
Everything you need to know to change the size of your photos on your Mac
PDF download Download Article

Resizing an image on your Mac is simple with Preview, a free image utility that comes pre-installed on macOS. Preview helps you crop images easily and adjust their dimensions without having to install additional software. Learn how to gain control over the size of your photos, remove unwanted areas, and adjust the resolution for various uses with Preview. We’ll also tell you about some third-party tools you can try.

Quick Steps

  1. Open the image you want to resize in Preview.
  2. Click the Markup button.
  3. Click the Adjust Size button.
  4. Enter your desired height, width, and resolution for your image.
  5. Click OK to apply your changes.
Method 1
Method 1 of 4:

Resizing an Image in Preview

PDF download Download Article
  1. This method will help you change the size of the entire image. If you want to crop out a part of the image to resize, see Cropping an Image in Preview .
    • To search for an image name or tag, open Finder , then click the magnifying glass icon in the menu bar. Type in your search criteria and press ⏎ Return to show your results.
  2. This will open the image in Preview.
    • You can also Ctrl-click the image and select Open With and then Preview .
    Advertisement
  3. The
    Mac Preview Markup
    Markup button looks like a circle with a pencil tip inside. This will launch a new toolbar at the top of the Preview window. [1]
    • If you don’t see this button, you may need to press the double arrow icon at the far-right side of the toolbar at the top of the window to see more tools. You can also expand the window to display more tools.
    • Alternatively, click the View menu at the top of the screen and select Show Markup Toolbar .
  4. You’ll see this in the toolbar that opens when you expand the Markup menu. It looks like a rectangle with a smaller, divided rectangle inside it.
    • You can also click Tools > Adjust Size… in the menu bar at the top of the screen.
  5. Resolution is measured in pixels per inch (also called “dots per inch” or “dpi”). You can also use the drop-down menu to change it to pixels per centimeter instead. If you plan to print your image or simply want it to retain as much of its quality as possible, consider raising the resolution.
    • If your image is for the web or for use in an app like Facebook, the default (72) is fine. If you start with a higher resolution, reducing it will give you a smaller file size.
    • If you plan to print your image in a high-quality format, such as for advertisements or other business communications, set it to at least 600. Note: this will raise the size of the file significantly.
    • To print glossy photos, 300 will suffice. The file size will be much larger than that of a default 72 dpi image, but the final quality will be worth it.
  6. The larger the width and height, the larger the file size.
    • The dropdown next to the Width and Height boxes offers several scale options. For example, you can select inches , a metric scale like cm or mm , a digital unit like pixels , or even percent to resize by a percentage of the current image size.
    • You can also select from several preset sizes in the Fit into dropdown at the top of the window.
  7. This is optional, but you can use this option to make sure that setting the width also modifies the height. This ensures that the image retains its original proportions.
  8. If you want to shrink your image without any loss of detail, make sure the box next to Resample image is checked.
  9. If you are dissatisfied with the changes, press ⌘ Cmd + Z to undo them.
    • Before you click OK , take a look at the information in the Resulting Size section of the Adjust Size window. This will tell you both the new dimensions of the image and the new file size.
  10. Once you’re done resizing the image, remember to save your work.
    • If you want to save this newly resized image as a brand new file, Click File , then Save As , then choose a new filename.
    • If you realize you made a mistake after saving, click Revert To in the File menu and select Browse All Versions… Choose a previous version of the image to which you would like to revert.
  11. If you want to resize several images in a batch, you can easily do so in Preview. Here’s how:
    • Open an image, then go to View > Thumbnails . Drag all the images you want to edit into the sidebar on the left. [2]
    • Select all the images in the sidebar by clicking one of them and pressing Command-A .
    • Go to Tools > Adjust Size… in the menu bar at the top of the screen. Resize the images using the settings in the window that pops up.
    12. Advertisement
Method 2
Method 2 of 4:

Cropping an Image in Preview

PDF download Download Article
  1. The icon is in the toolbar at the top of the Preview window. It looks like this:
    Mac Preview Markup
  2. Click the dotted rectangle icon in the editing toolbar, then select Rectangular Selection . [3]
  3. Once you let go of the mouse button, you will see the dotted rectangle appear over a portion of the image you selected.
  4. This will remove all parts of the image that are outside of the rectangular selection. You can also press Command-K to crop the selection.
    • If you want to save the cropped area as a brand new file (and keep the entire image from which you cropped it), Click File , then Save As , then choose a new filename.
    • To revert the image to a previous version after saving, click File , then Revert To , and select Browse All Versions… Now, choose an older version of the image.
    6. Advertisement
Method 3
Method 3 of 4:

Changing an Image File Size in Preview

PDF download Download Article
  1. If you want to change an image’s file size without changing its dimensions, you can do so by reducing the resolution. To start, open the image in Preview. Control-click the image in Finder and select Open with > Preview , or open Preview and select File > Open… to browse for the image.
  2. Click the
    Mac Preview Markup
    Markup button in the toolbar at the top of the image window.
  3. It looks like a rectangle with a smaller, divided rectangle inside it. [4]
    • You can also go to Tools > Adjust Size… in the menu bar at the top of the screen.
  4. This will help ensure that you don’t lose too much detail when you reduce the image size.
  5. This will reduce the quality of your image, but it will also make the file size smaller. If you don’t change any other settings, the dimensions of your image should remain the same.
    • You’ll see the new file size displayed at the bottom of the Adjust Size window, under the header that says “Resulting Size”.
    6. Advertisement
Method 4
Method 4 of 4:

Using Third-Party Tools

PDF download Download Article
  1. While you can easily resize images using the built-in tools on your Mac, Preview isn’t the only option. You can also resize or crop images in most photo editing software. These apps may offer more advanced resizing options that you can’t get in Preview (such as changing the interpolation mode so you have more control over the quality of the resized image). If you want a free app that can do most of the things Photoshop can do, download GIMP .
    • The right way to scale an image varies from one app to another, but the basics are usually pretty similar. For instance, in GIMP: [5]
      • Open your image and select Image > Scale Image… .
      • Enter your desired dimensions in the Width and Height boxes. You can also change the scale with the dropdown on the right.
      • Type your desired resolution into the X resolution and Y resolution boxes.
      • Click the chains between the size and resolution boxes if you want to constrain the proportions of your image.
      • When you’re done, click Scale .
    • These apps also allow you to export certain file types (such as JPEG) at different quality levels, so you can create a larger or smaller file size without changing the image's dimensions.
  2. If you’re looking for a quick and simple solution, there are several online tools that will allow you to resize images for free. To use most of these tools, you simply drag and drop your image into a box on the webpage, choose an output size, and then download the resized image.
    3. Advertisement

Expert Q&A

Search
Add New Question
  • Question
    Should I resize an image for editing?
    Stephen Cardone
    Professional Photographer
    Stephen Cardone is the COO of NY Headshots, a New York City-based studio that specializes in shooting and producing headshots for individuals and businesses. Stephen has over four years of professional photography experience and over six years of documentary filmmaking experience. Stephen also works extensively as a photographer at NY Headshots. His work includes events, environmental photography, as well as headshots for actors, models, and corporate. He holds a BA in Non-fiction Writing from The New School.
    Stephen Cardone
    Professional Photographer
    Expert Answer
    Try resize it as little as possible, as you don't want to limit the photo during the editing process—you want to be working with the maximum amount of information available.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
    Yes No
    Not Helpful 0 Helpful 0
  • Question
    When I make changes to the image, it does not appear to keep the changes. The image is still at the wrong dpi as well.
    Community Answer
    You can try to export the image to different file formats by going to the menu bar and click on "File>Export." This will create a new file in the type you specified with the resized settings. Be sure you are opening the file you duplicated rather than the original file if they are placed in different locations.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
    Yes No
    Not Helpful 2 Helpful 9
  • Question
    What do I do if my picture gets rotated or flipped when I upload it to my Mac?
    Nanavi
    Community Answer
    There are options to edit on System preference -> Track pad. Go through options to get the settings and your picture correct.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
    Yes No
    Not Helpful 0 Helpful 1
See more answers
Ask a Question
200 characters left
Include your email address to get a message when this question is answered.
Submit
      Advertisement

      Tips

      Submit a Tip
      All tip submissions are carefully reviewed before being published
      Name
      Please provide your name and last initial
      Submit
      Thanks for submitting a tip for review!

      You Might Also Like

      How to
      Install macOS on a Windows PC
      How to
      Show Hidden Files and Folders on a Mac: 4 Simple Methods
      How to
      Take a Screenshot on a Mac: Complete Guide
      The Easiest Ways to Download YouTube Videos on macOS
      How to
      Safely Clear Cached Files on Your Mac
      How to
      Set up VNC on a Mac and Fix Common Issues
      How to
      Open RAR Files on Mac OS X: Free Apps, Online Tools, & More
      How to
      Reset a Lost Admin Password on Mac OS X
      3 Easy Ways to Allow Mac Apps from Unknown Developers
      How to
      Insert a Signature in Pages on Mac
      3 Ways to Add & Remove Apps from a Mac's Dock
      How to
      Quit an Unresponsive App on a Mac: Step-by-Step Guide
      How to
      Connect Airport Time Capsule to Mac
      How to
      Create a Backup for a Mac Without Time Machine
      Advertisement

      References

      1. ↑ https://support.apple.com/guide/preview/crop-resize-or-rotate-an-image-prvw2015/mac
      2. ↑ https://support.apple.com/guide/preview/display-several-files-in-one-preview-window-prvw1085/11.0/mac/14.0
      3. ↑ https://support.apple.com/guide/preview/crop-resize-or-rotate-an-image-prvw2015/mac
      4. ↑ https://support.apple.com/guide/preview/crop-resize-or-rotate-an-image-prvw2015/mac
      5. ↑ https://www.gimp.org/tutorials/GIMP_Quickies/

      About This Article

      In other languages
      Thanks to all authors for creating a page that has been read 1,190,826 times.

      Reader Success Stories

      • Samantha Shucavage

        Aug 4, 2017

        "This was so helpful! I had been trying for hours to set up my email signature through Mail on my Mac, which ..." more
        Rated this article:
      More reader stories Hide reader stories
      Share your story

      Is this article up to date?

      Advertisement