Calculations allow you to create custom reporting measurements to track the performance of a Campaign. A Calculation combines the available visit data with active Metric data that SiteSpect collects. Calculation Equations use standard SQL Operators to join elements.

Like all other Metrics, Calculations automatically calculate the sum, average, percent difference, percent significance, and other measurements in reports. Calculations, such as **Totals** and **Uniques**, perform calculations on either a per-visit or per-user basis depending on the view you choose in the report.

For example, you may have several standard Metrics, each of which measures a conversion event of some kind. You can use a Calculation that sums all the conversion events for a single visit (or a single user). The reports then calculate the average number of conversions per visit (or user). To define this Calculation:

- Select the first conversion
**Metric**from the**Add a Variable**list. - Type the sum operator
**+**(plus sign). Learn more about available Operators. - Select the second conversion
**Metric**from the**Add a Variable**list. Repeat these steps until the equation includes all necessary Metrics.

**Note:**If the value of any Metric in your equation is NULL, the rest of the Calculation is NULL.

The Equation field works as follows:

- To add a variable to the Equation, select it from the
**Add a Variable**list. - To delete a variable from the Equation, click the small
**x**that appears at the end of the variable. - Use the Operators to join variables.
- If your browser permits, you can click and drag a variable to a new location within the Equation.