Graphics are key to getting engagement on Facebook, but if you’re using them you’ve probably come up against the frustrating problem of the myriad image sizes that Facebook uses, and Facebook’s tendency to constantly tweak them.
Photographer David Coleman has an exhaustive 2014 Facebook Photos Size Guide on his blog, that covers everything you could possibly need. Highly useful.
Unfortunately there are not many guidelines available for the best photo sizes for mobile, as the various devices display wildly different sizes.
If you’re planning a mobile campaign or think that your graphic will be particularly relevant to people on smartphones, you can test it on your own phone. Post the image to your personal profile and set the sharing to ‘Only Me’, then view it on your phone’s Facebook app. Keep the graphic simple and post the detailed stuff in the caption.