IllustrationYou are viewing the macOS 26 version of this guide, recorded on macOS Tahoe 26 (MacBook Pro) on 9 November 2026. It is kept as it was and not updated. See the macOS 27 version.
howtosimply.com/guides/how-to-resize-an-image-on-a-mac-with-preview/ · Checked 9 November 2026 · MacBook Pro · macOS Tahoe 26
In this guide
Open the picture in Preview, choose Tools, Adjust Size, type a new width or height and click OK. Keep Scale proportionally ticked so the picture is not stretched. The window shows the resulting file size before you confirm.
6 of 7 steps with real screenshots · 1 official source below
- Device
- Mac
- Shown on
- macOS Tahoe 26 (MacBook Pro)
- App
- Preview
- Real screenshots
- 6 of 7 steps
- Checked
- 9 November 2026
- Sources
- 1 official, linked below
Step by step
Work on a copy
Preview saves changes into the file automatically. If you want to keep the original, select the file in Finder first and press Command + D to duplicate it.
Tap the picture to see it full size Open the picture in Preview
Double-click the file. If it opens in another app, Control-click it and choose Open With, Preview.
Tap the picture to see it full size Choose Tools, Adjust Size
The same command is behind the Adjust Size button in the Markup toolbar.
Tap the picture to see it full size Enter the new size
Type a width or a height, or choose a ready-made size from the Fit into menu. To shrink by a percentage, change the unit to percent.
Tap the picture to see it full size Keep the proportions
Leave Scale proportionally ticked. Then you only type one value and Preview works out the other.
Tap the picture to see it full size Check the resulting size and click OK
The bottom of the window shows the new file size. Click OK, and the picture is resized.
Tap the picture to see it full size Resize several pictures at once
Select all the files in Finder and open them together, so that they appear in one Preview window. Select them all in the sidebar with Command + A, then choose Tools, Adjust Size.
About this guide
Preview, the app that opens pictures on every Mac, can make an image smaller in pixels and in file size. That is enough for email attachments, application portals and websites. No extra software is needed.
These steps are for recent versions of macOS.
Some pictures are simplified diagrams of the screen, not screenshots.
Good to know
To make a file smaller without changing how large it prints, tick Resample image and lower the Resolution value instead.
Enlarging a small picture does not add detail. It only becomes blurry.
iPhone photos in HEIC format: how to convert HEIC photos to JPG on a Mac.
In short: Duplicate the file, open it in Preview, Tools, Adjust Size, type the width, keep Scale proportionally, OK.
Links checked in October 2026. Menus and features can change after software updates. These steps match the version named at the top.
📷 Camera Lab: the same 6 scenes photographed with 11 phones, side by side.
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