← All guides

How to resize an image on a Mac

Change a picture's width and height on a Mac with Preview's Adjust Size, one Terminal command, or a free browser tool, without stretching it.

The problem

A form wants a photo no wider than 600 pixels, a website wants 1200, and the picture from your phone is 4000 pixels and several megabytes.

How do I resize a picture on a Mac?

  1. Open the image in Preview and choose Tools > Adjust Size.
  2. Set the units to pixels and keep Scale proportionally ticked.
  3. Type the new width; the height follows.
  4. Click OK, then save, or use File > Export to keep the original as it was.

How do I resize many images at once on a Mac?

In Terminal, sips resizes in place or to a new file. -Z fits the longest side to the number you give and keeps the proportions:

sips -Z 1200 photo.jpg --out photo-1200.jpg

Or open them all in Preview, select them in the sidebar, and use Adjust Size once for all of them.

How much smaller does resizing make a file?

A lot, because the file size follows the number of pixels. We resized a 6016 by 6016 JPEG of 4.1 MB to 2000 pixels with sips -Z 2000: it came out at 327 KB, about a twelfth of the size.

How do I resize an image without stretching it?

Keep Scale proportionally ticked in Preview, or use sips -Z, which always keeps the proportions. To make a picture a different shape, crop it instead of resizing it.

Our take

Resize to the size it will be shown at, not smaller. A photo for a 1200 pixel wide page needs 1200 pixels, perhaps 2400 for sharp screens; going further saves little and makes the picture soft when someone zooms.

In your browser

Our free image resizer resizes many pictures at once, without uploading them.

Measured on 16 October 2026 on a MacBook Air (M1), macOS 27.0.1, with sips -Z 2000 on a 6016 by 6016 JPEG made from a system desktop picture.

Questions

How do I resize a picture on a Mac?

Open it in Preview, choose Tools > Adjust Size, type the new width with Scale proportionally ticked, and save.

How do I resize an image without stretching it?

Keep Scale proportionally ticked in Preview, or use sips -Z, which keeps the proportions.

More guides