How do I change a photo to 200x240 pixels

If the photo is in your Photos Library, you can use a custom size when exporting the photo from Photos:

• First crop the photo in Photos to the aspect ratio of 10 to 12.
• Then use File > Export > Export .. photo.
• In the Export panel select a custom size like this:

Before you export the photo as léonie described you should crop the image to an aspect ration of 240:200 or 1.2:1. Then export with the max dimension at 240 pixels.

Otherwise the export might crop out part of the image you don't want copped out. This is more likely with photos that have more than just a head shot in it.

Had an iPad but never used it for posting or sending emails. Can't handle the screen keyboard. Have to have a regular keyboard. Hate trying to send messages or emails with my iPhone. Among other issues is my fingers are too fat for the keys on the iPhone and I get too many errors and then really back auto spelling corrections. Gets embarrassing sometimes. 😟

Use Preview

http://osxdaily.com/2016/09/05/how-to-resize-photo-mac/

I think, BSPBSP has a photo in portrait orientation, OT, that is why I recommended cropping to an aspect ratio of 10 to 12, will give the same result as 20 to 24. 😁

Perhaps I misread the post.

I'm still asleep today. Missed the 10 to 12 statement. My bad. 😊

But you explained nicely, why the cropping is recommended 🙂

I am lazy and an bit short, when I have only my iPad for posting!

An iPad is nice while I'm commuting, on long, boring train rides. But after having been reduced to an iPad, I am really appreciating my Mac!