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Optimizely Knowledge Base

Create a metric in Optimizely

  • Understand the different components of a metric in Optimizely
  • Create a metric in Optimizely's metric builder
  • Add a metric to your Optimizely experiments

Optimizely’s natural-language metrics builder lets you quickly define and add metrics to your experiments and campaigns. It works by asking you to define a small set of parameters that tell Optimizely how to measure and report the results of your experiment or campaign. These parameters include the winning direction (increase or decrease), what you want to measure (the numerator), and the rate at which you want to measure it (the denominator).

The process of building a metric using the metrics builder is straightforward.


  1. From the Experiments tab, open the experiment you want to work with.

  2. Click the Metrics button to open the Metrics modal.

  3. Choose an event from the list to be your metric.

  4. Choose a name for your metric and set its winning directionnumerator, and denominator.

Optimizely offers several pre-built metrics, as well as a flexible numerator called total value. If you're not sure which metric to choose, read our Knowledge Base article on when to use each type of metric for deeper explanations and use cases.

To learn how to edit your metrics once you've built them, see our Knowledge Base article.

The metrics builder

The metrics builder is the interface within Optimizely that enables you to create your own metrics.


You can only build metrics in Optimizely if your role is authorized to create and edit campaigns and experiments--that means administrator, editor or project owner. See this article for more details.

Several metric types have additional requirements you'll need to be aware of prior to using them:

Be sure to read those articles for more information.

Winning direction

When you set a metric's winning direction parameter, you are telling Optimizely what kind of change you hope to see: an increase in your metric, or a decrease. In most experiments and campaigns, you will want to see your metrics increase. However, for some metrics—like bounce rate, Cancel button conversions, or cart abandonment—a lower value (i.e., negative lift) would be more desirable. 


The metrics builder offer six different types of metrics templates. These types are also called numerators. You should select your metric's numerator based on the specific questions you want your experiment to answer: 

  • Unique conversions: the number of visitors with at least one conversion

  • Total conversions: the total number of conversions

  • Bounce Rate: the total number of times where the page being viewed is the first and only page the visitor sees before leaving your site

  • Exit Rate: the total number of times where the page being viewed is the last page the visitor sees before leaving your site

  • Total revenue: total revenue generated (you will have to set up revenue tracking before using the total revenue metric)

  • Total value: the total of any other numerical value (check out our article on total value use cases)

For more details on each metric type, see our article on when to use each type of metric in Optimizely.

If you are using total revenue or total value as your numerator, you will need to complete an additional step. The additional step for total revenue is not the same as the additional step for total value. Make sure you are reading the correct section.


The metrics builder's denominators can also be thought of as the rate at which your metric measures its numerator. For example, you could measure unique conversions per session, or total revenue per conversion.

Because of the inherent differences between metric types, and the differences between personalization campaigns and experiments, not every denominator works with every numerator.

Numerators Experiment type Possible denominators
Per visitor Per session Per conversion
Unique conversions and total conversions Personalization campaign    
Unique conversions and total conversions Experiment    
Bounce rates and exits rates Any   *  
Total revenue and total value Personalization campaign  
Total revenue and total value Experiment  

When you run an experiment with many variations and metrics, there’s a greater chance that some of them will give false positive results. The Optimizely Stats Engine uses false discovery rate control to address this issue and reduce your chance of making an incorrect business decision or implementing a false positive among conclusive results. To learn how Stats Engine prioritizes primary and secondary metrics and monitoring goals, see Stats Engine approach to metrics and goals.