AVERAGEIFS(average_range, criteria_range1, criteria1 [,criteria_range2, criteria2]) 
Returns the arithmetic mean of all the numbers in a range that satisfies multiple conditions. 
average_range  The actual cells to average. 
criteria_range1  The range of cells you want evaluated. 
criteria1  The expression that contains the criteria. 
criteria_range2  (Optional) The range of cells you want evaluated. 
criteria2  (Optional) The expression that contains the criteria. 
* Added in Excel 2007.
* This function includes hidden rows.
* This function uses the actual cell values and not the displayed formatted values.
* This function can handle full column references ($A:$A) very efficiently because it ignores empty cells.
* All the "criteria_range" ranges must be the same size and shape as "criteria_range1"
* If "average_range" is blank or a text value, then #DIV/0! is returned.
* If "average_range" contains any cells that are not numbers, then #DIV/0! is returned.
* If "criteria" contains any cells that are empty, then they are treated as 0.
* If there are no cells that meet the criteria, then #DIV/0! is returned.
* Arguments that are logical values are excluded.
* Arguments that are text are excluded.
* Arguments that are zero are included.
* If any cells reference are empty, then theses are ??
* You can use wildcard characters (?) and (*).
* Any empty cells are considered equivalent to a 0 value.
* You can have up to 127 different criteria.
* You can use the AVERAGE function to return the arithmetic mean with no conditions.
* You can use the AVERAGEA function to include logical values and text in the denominator.
* You can use the AVERAGEIF function to satisfy one condition.
* This is similar to the COUNTIFS function.
* This is similar to the MAXIFS function.
* This is similar to the MINIFS function.
* This is similar to the SUMIFS function.
* For the Microsoft documentation refer to support.office.com

1  What is the average of all the numbers in the range "C1:C5" that have "Barry" in the range "B1:B5",
2  What is the average of all the numbers in the range "C1:C5" that have "Barry" in the range "B1:B5". Notice that prefixing the condition with an equal sign means the same thing.
3  What is the average of all the numbers in the range "C1:C5" that have "Simon" in the range "B1:B5".
4  What is the average of all the numbers in the range "C1:C5" that have "Barry" in the range "B1:B5" and have a value not equal to 20 in the range "C1:C5".
5  What is the average of all the numbers in the range "C1:C5" that have "Barry" in the range "B1:B5" and have a value equal to 20 in the range "C1:C5".
6  What is the average of all the numbers in the range "C1:C5" that have "Barry" in the range "B1:B5" and have a value greater than the value in cell "C3" in the range "C1:C5".
6  include wildcards and date filtering.
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