Often you may want to sum the values of some dataset in Excel based on week.

For example, suppose we have the following dataset and we’d like to sum the total sales by week:

The following step-by-step example shows how to do so.

**Step 1: Enter the Data**

First, enter the data values into Excel:

**Step 2: Extract the Week Number from Dates**

Next, we need to use the **=WEEKNUM()** function to extract the week number from each date.

In our example, we’ll type the following formula in cell **D2**:

=WEEKNUM(A2)

We’ll then drag and fill this formula down to every remaining cell in column D:

**Step 3: Find the Unique Weeks**

Next, we need to use the **=UNIQUE()** function to produce a list of unique week numbers.

In our example, we’ll type the following formula in cell **F2**:

=UNIQUE(D2:D10)

This will produce a list of unique week numbers:

**Step 4: Find the Sum by Week**

Next, we will use the **SUMIF(range, criterion, sum_range)** function to find the sum of the sales made during each week.

In our example, we’ll type the following formula in cell **G2**:

=SUMIF($D$2:$D$10, F2, $B$2:$B$10)

We’ll then drag and fill this formula down to the remaining cells in column G:

This tells us:

- There were
**40**total sales made in the first week of the year. - There were
**77**total sales made in the second week of the year. - There were
**38**total sales made in the third week of the year.

And so on.

**Additional Resources**

The following tutorials explain how to perform other common tasks in Excel:

How to Sum by Month in Excel

How to Sum by Category in Excel

How to Sum Across Multiple Sheets in Excel