# Add Calculated Metrics

You can add a calculated metric to a model by writing an MDX formula that operates on existing metrics already defined in the model.

Calculated metric formulas are written in MDX syntax, but only support a small subset of MDX functions and operators. They can only operate on the existing metrics in the model, and must return a numeric value. You can do simple math operations to combine metrics, or simple comparison operations to return a given metric value when certain conditions are met.

*Note:* AtScale recommends using Dimension Calculation Groups, which allows you to reduce the number of calculated metrics in a model.

# Before You Begin

If you have experience with creating formulas in Tableau, you need to consider that the formulas for calculated metrics in AtScale are somewhat different. For details, see Calculated metric syntax.

The syntax validation mechanism used when entering the MDX formula detects cases where the equals operator is used incorrectly for comparing the CurrentMember function to a scalar value. Also, it displays a warning about using the

`[Dimension].[Hierarchy].[Level].CurrentMember`syntax.If you need to disable these syntax checks, you can do so using the

`query.language.mdx.currentMember.allowLegacySyntax`engine setting. For details, see Changing Engine Settings.

# Procedure

To add a calculated metric:

In Design Center, open the model you want to add a calculated metric to.

If you want to reference a particular metric in the calculated metric, determine its unique name.

*Note:*If you plan to use the CURRENTMEMBER.NAME function in your formula, you will also need to get the dimension attribute's unique name. Pay attention to role-playing dimensions, as their unique names have a prefix that proceeds the attribute's unique name.Click the plus icon at the top of the page and select

**New Calculation**. The**Edit Calculated Measure**panel opens.Complete the following fields:

**Display Name**: The name of the calculated metric as it appears in AtScale.**Unique Name**: The unique name of the calculated metric. This must be unique across all repositories and subrepositories.**Description**: A description of the calculated metric.**Visible in BI Tool**: Determines whether the calculated metric appears in BI tools.**Formatting**: The format for results of queries against the calculated metric. If you select**Custom**, you must also enter a custom format.

In the

**Formula**field, enter the MDX formula you want to use. Be aware of the following:- The formula must return a numeric value.
- When using Power BI, AtScale recommends using the hierarchy name in the expression, rather than the dimension name.
- You cannot combine metrics from multiple fact tables in the same formula if using CURRENTMEMBER.NAME in your formula.
- You can only evaluate dimensions in a calculated metric formula with metrics from a single fact table.

Click

**TEST MDX SYNTAX**to validate your formula.Click

**Apply**.

The new calculated metric appears in the `calculations/` folder in the **Repo Browser** and can be added to models as needed.

# MDX reference

For details about the MDX functions and operators allowed in a calculated metric formula, see MDX Reference.