The Instagram Profile Picture size (320×320px)
Instagram stores profile pictures at 320x320 pixels, and even though the avatar is displayed much smaller in the feed and comments, uploading a clean square at this resolution keeps it sharp when viewers tap through to your profile. Feeding a properly sized image avoids the soft, blurry look that comes from letting the app upscale a tiny source.
The crucial detail is that Instagram displays every profile picture inside a circle. Your 1:1 square gets masked, so the corners are cut off entirely. Any logo, face, or symbol pushed toward a corner will be clipped, which is why centered, roughly circular compositions read best here.
Because it renders so small, a busy avatar becomes an unrecognizable blob at feed scale. Simple, high-contrast marks win: a single face, a bold logo, or one clear icon. Test how it looks shrunk down before committing, since the whole point of an avatar is instant recognition in a tiny circle next to your posts and Stories.