Cost per result is a metric that helps you to determine the consequences of your advertisement.
Perhaps you’ve designed a campaign to generate page likes. In that case, your cost per result will report the cost of each page like generated by your ads.
Some results are the subject of attribution windows. It’s possible, for example, that a user may see your ad and click on it a few days later. In that case, Facebook will adjust your cost per result based on the attribution window that you have selected.
Cost Per Result is influenced by a number of different factors including who you are targeting, how you have chosen to optimize your ad, the type of creative you’re using, when you’re running your ad and how much you’re bidding for each engagement. When your ads are relevant to the users you are targeting, you will generally get a much lower cost per result than you would otherwise.
This metric is useful because it can help you to quickly determine how cost effectively your ads are performing. It can be used to calculate the return on your advertising spend or to help you determine how to bid on ads you run in the future.
Facebook calculates your Cost Per Result by taking the total amount you’ve spent and dividing it by the number of results you have generated.