850px x 315px. Not a bad size to advertise yourself on your page, but hold your horses Nelly! They've got some rules and regulations that you need to be aware of.
Facebook Cover photos cannot include:-Price or purchase information, such as "40% off" or "Download it at our website".
-Contact information such as a website address, email, mailing address, or information that should go in your Page’s "About" section.
-References to Facebook features or actions, such as "Like" or "Share" or an arrow pointing from the cover photo to any of these features.
-Calls to action, such as "Get it now' or "Tell your friends".
-Covers must not be false, deceptive or misleading, and must not infringe on third parties' intellectual property.