How to crop in Photos (for desktop) to specific dimensions/pixels?

You can resize your image files with the demo version of GraphicConverter. You can batch resize photos to 600 x 270 by putting them in a folder and adding the folder to GraphicConverter. Then select all of the folders and select the Resize ➙ Quickscale menu option.

That will give you this window where you set the dimensions of the resulting images:

Click OK and sub folder and you'll get a subfolder with the reduced sized files.

[Edited by Moderator]

RoseCahalan wrote: …Here's what I see when I enter 60x27 for aspect ratio...doesn't look right.

That makes no sense! Here's what I get:

which looks just right. It's almost like yours is seeing a decimal point, or something that we don't.It certainly looks the same! Did you try messing with it--try 60x30 or 61x28, just to see if you can tell what's going on? This was a normal 4x3 picture to begin with, right?

What you did was clever, but way too much trouble!

If jiggering with it doesn't work, close and re-open Photos. If that doesn't work, then to narrow things down, try these steps:

• Restart the computer (of course)
• Re-start in Safe Mode. This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this: 

           Start up your Mac in safe mode - Apple Support 

• Use another library if you have one, or make a small test Library with a few pictures in it and see if the same thing happens. You can create a new Library by closing Photos and then option-clicking on the Photos icon.
• Make a new user and see if the same problem recurs with it.  This is a bit harder, because a new user can't access a different user's stuff. You would need to move your Library out of your own user's folder up to the general "Users" folder. 
• Rebuild your Photos Library--close Photos and re-launch by option-command-clicking the app icon. If you use iCloud Photos, it’s possible that this will cause a re-sync that lasts long enough to make you nervous.

The idea is to find out if the problem is with the Library, with your account, or with caches and login items, and stuff like that. One of these steps may fix the problem, but their failure to work also helps figure out what's happening.

Let me know!

One way, using Photos, would be to set a custom aspect ratio in Crop Mode:

I have mine set to 16x10, since that's the aspect ratio of my MacBook screen. You could use 600x270. But it would be the same as 60x27, or 20x9-- it sets the ratio, not the number of pixels.

Once that's set, when you use File>Export>Export nn Photos, you get this:

Photos Export doesn't let you change the aspect ratio on the fly, since you need to see what that looks like first.

Exported pictures can have their own quality, format, and file name, including an index for order, so it's a great way to produce picture files.

Is this what you need?

How much free storage do you have on your Mac?

System Settings>General>Storage.

On my 1 TB MacAir I had really crazy stuff going on when I had only 130 GB free. It cleared up when I got over 150 GB free.

100GB out of what? Again, I had random troubles with less than 150 GB free. I'm using a MacBook right now, macOS 15.6, and it works fine, so what else might be different?

Using flaky 3rd party apps, like cleaners or VPNs, can mess things up, but the steps you went through would show that. My experience is that low storage isn't exposed by those tests.