Report Builder functions - Var function in a paginated report (Report Builder)
Applies to: 
Microsoft Report Builder (SSRS)
Power BI Report Builder
Report Designer in SQL Server Data Tools
Returns the variance of all non-null numeric values specified by the expression, evaluated in the given scope in a paginated report.
Note
You can create and modify paginated report definition (.rdl) files in Microsoft Report Builder, Power BI Report Builder, and in Report Designer in SQL Server Data Tools.
Syntax
Var(expression, scope, recursive)
Parameters
expression
(Integer or Float) The expression on which to perform the aggregation.
scope
(String) Optional. A constant that is the name of a dataset, group, or data region that contains the report items to which to apply the aggregate function. If scope is not specified, the current scope is used.
recursive
(Enumerated Type) Optional. Simple (default) or RdlRecursive. Specifies whether to perform the aggregation recursively.
Return Type
Returns a Decimal for decimal expressions and a Double for all other expressions.
Remarks
The set of data specified in the expression must have the same data type. To convert data that has multiple numeric data types to the same data type, use conversion functions like CInt, CDbl or CDec. For more information, see Type Conversion Functions.
The value of scope must be a string constant and cannot be an expression. For outer aggregates or aggregates that do not specify other aggregates, scope must refer to the current scope or a containing scope. For aggregates of aggregates, nested aggregates can specify a child scope.
Expression can contain calls to nested aggregate functions with the following exceptions and conditions:
Scope for nested aggregates must be the same as, or contained by, the scope of the outer aggregate. For all distinct scopes in the expression, one scope must be in a child relationship to all other scopes.
Scope for nested aggregates cannot be the name of a dataset.
Expression must not contain First, Last, Previous, or RunningValue functions.
Expression must not contain nested aggregates that specify recursive.
For more information, see Aggregate Functions Reference (Report Builder and SSRS) and Expression Scope for Totals, Aggregates, and Built-in Collections (Report Builder and SSRS).
For more information about recursive aggregates, see Creating Recursive Hierarchy Groups (Report Builder and SSRS).
Example
The following code example provides the variance of line item totals in the Order group or data region:
=Var(Fields!LineTotal.Value, "Order")