While the basic function of the Preview App on Mac is to view or open photos, it is also equipped with basic photo editing functions and can be used to resize photos.
The Preview App can be used resize photos that are located on the Desktop and also Resize Photos that are located in a Folder, just about anywhere on your Mac.
However, the Preview App cannot be used to resize photos that are located within the Photos App on your Mac, but you can get around this limitation by simply dragging Photos from Photo app to Desktop or any Folder on your Mac.
Resize Photos on Mac Using Preview App
Before going ahead with the steps to resize photos using Preview App, you need to be aware that once a photo is resized by the Preview App, it gets replaced by the resized photo.
Hence, if you want to keep the original photos, you need to make a copy of the original photos and use them for resizing.
1. Steps to Resize Photos on Mac Using Preview App
Follow the steps to Resize Photos on Mac using the Preview App.
1. Double click on the Photo that you want to Resize and allow it to open in the Preview app.
Note: If you have chosen a different App as your default Photo viewer, then right click on the photo and select Open with > Preview.
2. Once the Photo opens in the Preview App, click on Tools from the top menu bar of your Mac and then click on Adjust Size… option in the drop-down menu.
3. On the next screen, make sure that the option for Scale proportionally is checked (See image below)
Making the photo Scale proportionally ensures that any change that you make to the width of the photo will result in a proportional change in the height of the photo and vice-versa.
4. Next, you can choose whether you want to resize the image in pixels, centimeters, inches, percent, millimeters or points (See image below)
5. After selecting the resizing Unit, enter the new dimensions (Width or Height) for your image (See image below)
6. As you can see in the image above, the Preview App also allows you to change the Resolution of the images. This is helpful, in case you are also trying to reduce the size of the image.
Following are the recommended image resolutions for images, based on where you want to use them.
- 72 – 150 pixels – For images to be used on websites
- 240 – 300 – If you will be printing the image
- 600 – If you want the image to be of very high quality, as used in advertising and other uses where high resolution images are required.
7. Finally, click on the Ok button once you have finished resizing the photo (See image in step #5 above)
2. Resize Multiple Photos on Mac Using Preview App
The Preview app also allows you to resize multiple photos and you can use this option in case you have too many images to be resized.
1. Press the command key on the keyboard of your Mac and then select the Photos that you want to resize
Note: You could also quickly select photos by dragging your Mouse over them.
2. Once the Photos are selected, right-click on one of the photos that you want to resize and then select Open with > Preview option in the contextual menu (See image below).
Note: All selected Photos should open in a single window. Repeat the step above in case the selected Photos open in separate or multiple windows.
3. Next, click on Edit form the top menu bar on your Mac and then click on Select All option in the drop-down menu (See image below).
4. Once the Photos are selected, click on Tools from the top menu bar of your Mac and then click on Adjust Size… option in the dropdown menu.
5. On the next screen, make sure that the option to Scale Proportionally is selected and then enter the new size (Height or Width) for the Photos and click on the Ok button (See image below).
Image Size in Multiple Values?
While trying to Resize images on Mac, you may find the preview App displaying the words “Multiple Values” for Width, Height and Resolution Fields..
This is happening because the images that you have selected for resizing are in various units of measurement. In such cases, you can still resize images on your Mac by choosing to resize images in Percent (See image above).
3. Undo Photo Resize
In case you resized a photo to the wrong size, or simply do not like how the resized photo turned out, you can follow the steps below to undo the photo resize.
1. Double click on the Photo that you want to Undo the Resize for
2. Once the Photo opens in the Preview App, click on File from the top menu bar of your Mac and then click on Revert to > Browse all versions in the drop-down menu and contextual menus (See image below)
3. On the next screen, you will be able to browse and choose from the previous saved versions of the Photo stored on your Mac.
4. Simply, select the saved version of the photo that suits your requirements and then click on the Revert button.