Profile Picture : 720 px or 960 px and less than 100 KB.
Cover Page : viewable at 820 pixels wide by 312 pixels
feature phones : Must be at least 399 pixels wide and 150 pixels
Facebook ad : optimum image dimensions, are 476x714px.
Facebook event cover photo size is 1920 x 1080 pixels. This is a 16:9 ratio.
Facebook newsfeed 472x394px or 504x504px?