So you're putting on an event and you're ready to start marketing it on Facebook by creating a Facebook event, but you're unsure what size your event image should be. No worries, I'll help you out by covering some best practices.
Don't do this.
Whatever you do, don't just take a graphic that you designed for a completely different purpose and upload it as your Facebook event graphic. Doing this will likely make it hard for your audience to understand key details about your event, because they probably won't be able to read those details on your event graphic due to cropping issues. Instead, you should be intentional about designing a graphic that is specifically intended to be your Facebook event graphic when designing marketing material for your event.
What size should your Facebook event image be?
Your Facebook event image should be sized with the following specs: 1920 x 1005px 72 ppi. Sizing your event graphic in this way will ensure the graphic is legible and readable on most devices where Facebook is accessed.
What else should you consider?
Facebook is accessed from a wide variety of devices including desktop computers, iPhones, Android devices, etc. The sizing above will ensure a consistent experience across the board, but Facebook may crop your event graphic differently depending on where it's displayed within Facebook.
I sometimes find I need to slightly tweak the size and positions of elements within an event graphic to ensure an audience gets the best experience. I also keep in mind which devices people own the most of, i.e. iPhones, and most of the time design for that user experience.
Following these best practices and sizing requirements will ensure that your audience understands everything about your event.
Being intentional about your Facebook event graphic design will drastically increase the liklihood that your audience engages with your event, and attends the event in person when it becomes time.