Ok, Facebook Ad Manager does not provide a column for Engagement Rate but it can be calculated [Post Engagements / Reach]

I'll use a video post as a [hopefully, good] example to explain why the engagement rate can be totally different between Facebook Ad Manager and Facebook Insights.

Difference in engagement rate between Facebook Ad Manager and Facebook Insights

First, let's look at how engagements rate is calculated in Facebook Insights. The formula is Post Engagements divided by Post Reach.

1. Facebook Insights - Post Engagements: HOW IT'S CALCULATED

Total engagements = Post reactions + comments + shares + photo views + link clicks + other clicks + clicks-to-play video views.

Yes, Facebook Insights uses clicks-to-play video views and not all 3 second or more views.

Why? Because 3 second views includes clicks-to-play and autoplays [usually 95-97% of total views]. Adding 3 second views in post engagements would inflate the total engagements and produce a Cannes award winning engagement rate of 20-30%. Using clicks-to-play video views keeps the engagement rate to 1-2% [doesn't shock people and close to photo posts which get 4-5% engagement rate.

Ok, let's go to platform #2 , Facebook Ad Manager and try to look at the paid engagement rate for a post. Note: All metrics in Facebook Ad Manager are only paid, not organic + paid. 

ok, clicks-to-play video views used to be available in Facebook Ad Manager but looks like they removed it....

Fine, let's look at Post engagements in Ad Manager and divide it by (paid reach). 

2. Ad Manager - Post Engagements: HOW IT'S CALCULATED (Pasted straight from Facebook Ad Manager)

Post engagement includes all actions that people take involving your ads while they're running. Post engagements can include actions such as reacting to, commenting on or sharing the ad, claiming an offer, viewing a photo or video, or clicking on a link.

Viewing a photo or video...not, clicking to play a video! That's a huge difference.

Now that we've looked at how engagements are calculated in the platforms, let's use use some numbers to understand why creative and media agencies may show completely different numbers for the same post.

If you were to calculate engagement rate using Post Engagements from Facebook Ad Manager as your numerator, you'd end up with a whopping 22.4% engagement rate. Total engagements in Facebook Insights shows 2,890 while Ad Manager shows 22,133. The same post looked at in Facebook Insights yields a measly 2.9% engagement rate.

Now, let's go back to the first screenshot [No engagement rate metric in FB Ad Manager]. Seemed odd at first but not anymore, right? If this was added and the current calculations were used, video engagement rate data would completely overshadow photo content. Makes sense that they don't have it. 

However, the other important aspect to know here is that Cost Per Engagement is calculated using the 3 second video as part of post engagements. Using the Facebook Insights definition of engagements in mind while judging cost per engagement in Facebook Ad Manager can be misleading as cost per engagement will appear to be very low in Ad Manager.

Say, you spent $500 on that post. 

Dividing the Amount Spent by Total Post Engagements on both sides shows a $0.17 CPE [Cost Per Engagement] as per Facebook Insights but an awesome $0.02 CPE in Ad Manager! Problem. 

Now, you might ask - if it's a video post, why are looking at CPE and not CPV [Cost Per View]. Furthermore, why is the post promoted for engagement than views?

Having tested with both bidding models in Ad Manager, there are some benefits to a CPE model such as:

• A CPV model is an all - out instruction for Facebook Ads to maximize views. If your objective is views, fair enough. However, you must understand that the default bidding in CPV model is for 3 second views. So, if your video is 6 seconds long, you're looking at a 50% completion for when you pay for a view. If your video is a minute long, you're paying for views that complete 5% of your video. Facebook does offer another option to bid for 10 second views [will probably do a separate post on this]. For longer content, it might make sense to use this option as you're now getting more qualified audiences.

• Using a CPE model on a video post tells Facebook to maximize for engagements in the post [likes, comments, shares]. What this does is balance out the engagements [to a degree] between 3 second views, post likes, comments and shares. As it's a video post, no doubt, your maximum engagements in Ad Manager will still be 3 second views but you'll also see a fair bit of comments/shares [always welcome].

Hope this post helps. Let me know if I've missed something. 

-adil