Sometimes we may want to sum data by month but ignoring the year. For example, if we want to investigate which month has the top sales among several years, we may sum data by month but ignoring the year information. Actually, we can use formula based on **SUMPRODUCT **function and **MONTH** function to sum data for this instance. In this tutorial, we will introduce the usage of **SUMPRODUCT** function and **MONTH** function with simple description, formula explanation and necessary screenshots, also teach you the way to sum data by month ignoring year with above two functions.

**EXAMPLE**

Obviously, we have data for October in year 2020 and year 2019. We want to sum all items for October.

**FORMULA:**

In D2, enter the formula **=SUMPRODUCT((MONTH($A$2:$A$11)=10)*$B$2:$B$11)**.

**HOW THIS FORMULA WORKS:**

Inside of **SUMPRODUCT** function, we also use **MONTH** function in this instance. For **MONTH** function, the syntax is **MONTH(serial_number)**. For example, if A1 is 01/01/2020, then MONTH(A1) returns 1. This function returns the month serial number. So, if we want to find out date in date range belongs to October, we need to use MONTH($A$2:$A$11)=10 here, thus we can get an array as result.

Enter **=(MONTH(A2:A11)=10)** in D2 temporally. We get **TRUE** here, actually it only returns the first value of the array.

Move focus in formula bar, then press **F9** (on different version maybe **Fn+F9**). We can see the array is listed properly.

Update formula to **=–(MONTH(A2:A11)=10)**. Then **TRUE** or **FALSE** will convert to number properly.

Move focus in formula bar, then press **F9**.

For **SUMPRODUCT** function, the syntax is **SUMPRODUCT(array1,[array2],[array3],…)**. After learning **MONTH** function, we all know that **MONTH($A$2:$A$11)=10** it will return an array. As **SUMPRODUCT** function can returns the sum of an array, and $B$2:$B$11 is another array for saving amount, and data in this range is also the match value for each date in A column. so here we can use **=SUMPRODUCT ((MONTH($A$2:$A$11)=10)*$B$2:$B$11)** to sum data by month October properly. It equals to **{1;1;1;0;0;0;0;1;1;1}*{100;200;100;300;150;100;50;100;50;100}**, equivalent to **=SUMPRODUCT({100;200;100;0;0;0;0;100;50;100})**.

**RESULT:**

Now we can sum data by month ignoring the year properly.

### Related Functions

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