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Everything you need to know to change the size of your photos on your Mac
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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
- Open the image you want to resize in Preview.
- Click the Markup button.
- Click the Adjust Size button.
- Enter your desired height, width, and resolution for your image.
- Click OK to apply your changes.
Steps
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Navigate to the image you wish to resize. 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.
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Drag the image to the Preview icon in the Dock or Finder. This will open the image in Preview.
- You can also Ctrl-click the image and select Open With and then Preview .
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Click the Markup button to switch to Edit Mode. The 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] X Research source
- 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 .
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4Click the Adjust Size button. 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.
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Change the resolution. 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.
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Type your desired width and height in the designated boxes. 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.
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Place a check next to “Scale proportionally” to avoid warping the image. 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.
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8Check “Resample image” to avoid losing detail. If you want to shrink your image without any loss of detail, make sure the box next to Resample image is checked.
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Click OK to view the image at its new size. 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.
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Press ⌘ Command + S to save your changes. 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.
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11Resize multiple images at once with the Tools menu. 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] X Research source
- 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.
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Click the Markup icon to enter Edit Mode. The icon is in the toolbar at the top of the Preview window. It looks like this:
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Select Rectangular Selection from the selection menu. Click the dotted rectangle icon in the editing toolbar, then select Rectangular Selection . [3] X Research source
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Click and drag over the part of the image you want to keep. Once you let go of the mouse button, you will see the dotted rectangle appear over a portion of the image you selected.
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Click the Crop button. 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.
- The crop button looks like two angles overlapping to form a rectangle in the middle.
- You can resize the cropped area as you would any image .
- If you don’t want to save your changes, press ⌘ Cmd + Z to undo them.
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Press ⌘ Cmd + S to save your file.
- 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.
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1Open your image in Preview. 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.
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2Click the Markup tool. Click the Markup button in the toolbar at the top of the image window.
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3Select the Adjust Size tool. It looks like a rectangle with a smaller, divided rectangle inside it. [4] X Research source
- You can also go to Tools > Adjust Size… in the menu bar at the top of the screen.
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4Make sure the box next to “Resample image” is checked. This will help ensure that you don’t lose too much detail when you reduce the image size.
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5Enter a smaller number in the “Resolution” field. 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”.
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1Try an image editing app like Gimp or Photoshop. 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]
X
Research source
- 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.
- 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]
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Research source
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2Try an online image resizer. 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.
- Some of these tools offer size presets that are ideal for different uses (such as different social media platforms). They may also have additional editing tools.
- A couple of popular options include Adobe’s free image resize tool and this free Image Resizer from Shutterstock .
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Expert Q&A
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QuestionShould I resize an image for editing?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.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.
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QuestionWhen 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 AnswerYou 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.
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QuestionWhat do I do if my picture gets rotated or flipped when I upload it to my Mac?NanaviCommunity AnswerThere are options to edit on System preference -> Track pad. Go through options to get the settings and your picture correct.
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References
- ↑ https://support.apple.com/guide/preview/crop-resize-or-rotate-an-image-prvw2015/mac
- ↑ https://support.apple.com/guide/preview/display-several-files-in-one-preview-window-prvw1085/11.0/mac/14.0
- ↑ https://support.apple.com/guide/preview/crop-resize-or-rotate-an-image-prvw2015/mac
- ↑ https://support.apple.com/guide/preview/crop-resize-or-rotate-an-image-prvw2015/mac
- ↑ https://www.gimp.org/tutorials/GIMP_Quickies/
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