Resize an Image to Fit Your Mac Wallpaper Exactly

It depends on your display, so read it from your own Mac. Open System Settings > Displays. The resolution shown is the “looks like” size on a Retina screen. Or run this in Terminal.

system_profiler SPDisplaysDataType | grep Resolution

On my 14-inch MacBook Pro it printed 3024 x 1964 Retina. A wallpaper at that pixel size fills the screen. Larger is fine and can look sharper on a Retina panel, because macOS scales it down. Smaller gets enlarged and looks soft.

For reference, Apple’s own Mac Blue wallpaper file on my system measures 6016 x 6016 pixels, a square far larger than any screen, which shows that oversized is normal.

Often no. In System Settings > Wallpaper, choose Add Photo and pick your file. Then use the dropdown beside the preview to select Fill Screen, Fit to Screen, Stretch to Fill Screen, Center or Tile. Fill Screen scales the image to cover the screen and crops the overflow. That is the same result as the manual steps below, and macOS does it for you, though you do not control what is cropped.

Resize yourself when the image is huge and slows the file, when you want to choose the crop, or when you are making one version for several Macs.

1. Open the image in Preview and choose Tools > Adjust Size.
2. Set pixels. Keep Scale proportionally and Resample image on.
3. Make the image cover the screen. If the screen is wider in ratio than the image, set the width to your screen width (3024 in my case). Otherwise set the height.
4. Choose Tools > Rectangular Selection and drag a box with the screen ratio. Check the size readout.
5. Choose Tools > Crop, then File > Export.

Never uncheck Scale proportionally and type both numbers unless the shapes already match. That stretches the picture and faces look wrong.

Scale on the dimension that is the limiting one, then crop. For a 4000 x 3000 photo and a 3024 x 1964 screen, the width limits, so scale the longest edge to 3024 and center-crop the height.

sips -Z 3024 photo.jpg --out wall.jpg
sips --cropToHeightWidth 1964 3024 wall.jpg
sips -g pixelWidth -g pixelHeight wall.jpg

In my test the result read exactly 3024 x 1964. Two gotchas. A 4:3 photo needs this order, but a very wide panorama needs --resampleHeight 1964 first. And when I asked --cropToHeightWidth for a canvas larger than the image, sips padded it instead of failing: scaling by height only on my 4000 x 3000 test gave a 2618-wide image, and cropping to 3024 padded it. Always read the pixels back. Full flag reference: the sips command guide.

For a whole folder, wrap those two lines in a loop, or see batch resizing images with Automator.

Wallpaper sites often serve WebP or AVIF. macOS can open many of them, but Preview and the wallpaper picker handle them unevenly across versions. If an image will not set, convert it to JPEG first. Guides: WebP to JPG and AVIF to JPG.

If the image is too low-resolution for your display, enlarge it before you crop. Read increasing image resolution on a Mac and expect a softer result than a native-size image.

For a wallpaper, use macOS. Fill Screen in System Settings handles it, and Preview or sips handle the exact crop. Smol is not a cropping tool and has no control over the crop point.

Smol’s fill resize mode covers a box and crops to it, but you cannot choose what is cut off, so it only suits images where the middle is the subject. Smol makes sense if you have a folder of large wallpaper downloads in mixed formats (JPG, PNG, WebP, AVIF, HEIC) to shrink or convert in one pass, or an image that needs a 2x upscale first. It writes copies beside the originals by default, and nothing leaves the Mac. $29 once for one Mac: see pricing. Compared options are in the best image converter for Mac.