In the most basic sense Facebook calculates reach based on the number of times content is being displayed on other user's screens. Seems pretty straightforward but now we need to consider this – Facebook is a constantly growing platform. This means the amount of content (posts, images, videos etc.) is also growing. In this abundance of information it’s virtually impossible to serve users ALL THE CONTENT (especially since there’s an option to target sponsored posts). That’s why Zuckerberg & Co. developed an algorithm that controls what is being shown to users based on their previous activities.
In your Analytics module and Reports you’ll find several different ways reach is being measured but the one index you’ll probably want to check is *Total Reach*.
It’s divided into 3 categories – Organic, Viral and Paid.
Organic – your content has been shown to your fans directly, for free
Viral – your content is shown to Facebook users indirectly i.e. one of your fans liked your post and it’s being displayed to others in their newsfeed
Paid – content displayed to your audience through Facebook Ads (sponsored posts etc.)
This all doesn’t seem very complicated so far, right? Good, cause this is where the tricky bit starts:
Facebook delivers this information in 3 different increments – 1, 7 and 28 days.
So imagine you want to check what was your last 2 weeks' reach. You chose the time frame and now you can choose the increment. You’ll instantly notice that depending on your choice the data is going to be different. And this is why:
Reach is calculated basing on unique users. So If a user sees your content twice on one day and then twice the next day and you choose the reach in 1-day increments, the user will be counted once on day 1 and once on day 2.
If you choose 7-day or 28-day reach, that user will only be counted once in the 7-day and 28-day period, respectively. Regardless of the number of times they see your type of content.
This is precisely why one should never try to sum up reach metrics. The results will be simply false as depending on the chosen increment the system has a different understanding of what a unique user is.
Say you're trying to find out how did the reach looked like in the previous month. Unfortunately, there’s no way to precisely measure that, but you can set the time frame to the previous month and set the increment to 28 days. This will give you an idea of how many different (unique) users have seen your content (at least once).
Let’s recap then:
Reach is based on the content being shown to unique users
Organic reach is not equal to the number of your fans
Reach can be viewed in 1,7 and 28-day increments
Never try to sum up reach metrics – you’ll get false data!