Weighted Average

Also known as Weighted Mean or Weighted Arithmetic Mean
It is possible that some of your values may be more significant that others.
When this is the case we can apply a weighting to each value.
The weighted mean can be calculated with the following formula:

Lets consider four percentages where the first percentage must account for 40% of the total.
The remaining three percentages therefore must account for 20% each since the total must be 100%.

To calculate the weighted average in Excel, you must use the SUMPRODUCT and SUM functions using the following formula:

=SUMPRODUCT(X:X,X:X)/SUM(X:X) 

SUM page.
SUMPRODUCT page.