When working with data, it is common to have duplicate values in a range. Please check here to count the number of unique values in a range, or here to count cells without duplicates.

To calculate the numbers only with duplicates, you can use the unique count minus the number of cells without duplicates.

**Question: How many numbers are duplicates in column C?**

=SUMPRODUCT(1/COUNTIF(C2:C12, C2:C12)) - SUMPRODUCT(--(COUNTIF(C2:C12, C2:C12)=1))

=SUMPRODUCT(1/COUNTIF(C2:C12, C2:C12)) - SUMPRODUCT((COUNTIF(C2:C12, C2:C12)=1)*1)

The result returns 3, so three numbers are duplicates in column C.

**Explanation: **

- Step 1: SUMPRODUCT(1/COUNTIF(C2:C12, C2:C12)): To find the number of unique values in the range;
- Step 2: SUMPRODUCT((COUNTIF(C2:C12, C2:C12)=1)*1): To find the number of values without duplicates;
- Step 3: The difference will be the number of cells with duplicate values in the range.

To figure out the number of cells with duplicate values, you can use the following formula:

=COUNT(C2:C12) - SUMPRODUCT(--(COUNTIF(C2:C12, C2:C12)=1))

=COUNT(C2:C12) - SUMPRODUCT((COUNTIF(C2:C12, C2:C12)=1)*1)

The result returns 6, so six cells are duplicates.

**Notes: The SUMPRODUCT Function**

The SUMPRODUCT function adds all the multiplication results for all arrays.

**Formula:**

=SUMPRODUCT(array1, [array2], …)

**Explanations:**

– Array1 is required; the first array is to multiply and then add.

– Array2 is optional; the second array is to multiply and then add.