Instagram landscape size: 1080 by 566

The simplified ratio is genuinely ugly. The greatest common divisor of 1080 and 566 is only 2, so the fraction reduces no further than 540:283. That is not a clean ratio anyone designed; it is the pixel height that comes out of applying the platform's widest permitted shape, about 1.91:1, to a 1080 pixel width and rounding.

The shape is the same family as the 1200 by 630 link preview, which reduces to 40:21 and is also close to 1.91:1. Neither is 16:9, which is 1.78:1, and the difference is visible: a 16:9 image placed in a 1.91:1 frame loses a slice off the top and bottom, and the slice usually contains a chin or a horizon.

At 0.61 megapixels this is the smallest of the feed frames by a wide margin, and it also occupies the least vertical space on a phone. That combination is why landscape posts get less attention than portrait ones on a mobile first platform: they are literally smaller on the screen.

There is no preset at this size in the tools here. The cropper takes a custom width and height, so 1080 by 566 can be entered directly, and the resizer will accept the typed dimensions. Cropping to the shape first and resizing second avoids distorting the picture.