DAX function

AVERAGEX — DAX function reference

Mean of a per-row expression.

Syntax

dax

AVERAGEX(<table>, <expression>)

dax

AVERAGEX(Sales, Sales[Qty] * Sales[Price])

→ A number

CALCULATE triggers context transition so SUM re-evaluates for each OrderID rather than averaging individual line amounts.

dax

AVERAGEX(VALUES(Sales[OrderID]), CALCULATE(SUM(Sales[Amount])))

→ Average order value at the order level, not the line level

dax

AVERAGEX(Product, [Total Sales])

→ Average product's sales, including products that sold nothing

Without wrapping the expression in CALCULATE (or a measure reference, which implicitly wraps CALCULATE), AVERAGEX(VALUES(Sales[OrderID]), Sales[Amount]) just averages line amounts, not order totals.
Rows that evaluate to BLANK() are excluded from both the sum and the row count DAX uses internally, which can make the result differ from a hand-checked DIVIDE(SUM, COUNTROWS).

From Aggregations