profile image dimensions?

no matter what i do, my profile pic looks distorted. i'm trying very hard to be subjective about this and my profile pictures have more pixel distortion going on than other accounts. i've tried large dimensions, small dimensions... i've tried scaling the image inside instagram, not scaling. whats the rule of thumb?

http://www.goingsocial.ca/the-instagram-cheat-sheet-for-image-sizing-dimensions/

Check this out, it'll give you the correct dimensions