To check the file size of an image on your WordPress site, follow the procedures below. a) Log in to the backend dashboard of your WordPress site. b) Then, select Media among the menus on the dashboard’s left pane to go to the WordPress media library. c) In the WordPress media library, click the image you wish to see its file size. d) Finally, on the image's attachment details page, you will find the file size on the right pane.