Instagram feed posts: portrait 1080×1350 (4:5) takes the most screen, with square at 1080×1080 and landscape at 1080×566. This tool outputs the portrait spec, on the grounds that if you are going to the trouble of resizing at all you may as well have the extra height. Drop an image and it returns at exactly 1080×1350, cropped to cover the frame, with the crop position slider choosing which part of the source survives.
Why exact pixels matter here: Instagram re-compresses every upload, and an image at odd dimensions is scaled as well as compressed, taking two hits to quality where one would have done. Arriving at exactly 1080 wide leaves only the compression to do. For the same reason it is worth not compressing beforehand: this tool encodes at high quality and lets Instagram make that single pass.
Composition:
- Subjects in the upper two-thirds: feeds scroll fast; high placement reads in the half-second available.
- Avoid busy, dark bottoms: the likes/caption UI sits directly beneath the image in feed.
- The profile grid is 3:4: slightly taller than a 4:5 post, and grid thumbnails trim a sliver off each side. The post itself shows in full; keep faces and text clear of the left and right edges so the grid still reads.
- Reusing the image as a story? Stories are 9:16, a good deal taller, and Instagram will centre-crop to it without asking; the story resizer below lets you choose which part survives.
Drop several candidates, compare at output size, and post the winner. A 4:5 photograph takes up more of the feed than a square one, and that is the reason to bother cropping to it.