Prepare image dimensions for an Instagram post or another supported layout. Start from the photo's subject, not only its file size.
A square frame has a 1:1 aspect ratio; a portrait image uses a taller frame. Choosing an aspect ratio can crop content near the edges, particularly captions or faces.
Preview the resized image at a phone-screen size. Check whether essential details survive the crop and whether text remains legible after export.
Do not assume one dimension preset fits every placement. Confirm the current requirements for feed, story or reel in the publishing interface.