What is the formula count duplicate values

Answer

To count duplicate values in Excel, you can use a combination of functions depending on the level of detail you need. Duplicate values are entries that appear more than once in a range of cells.

1. Counting All Occurrences of a Specific Value

To count how many times a specific value appears in a range, use the COUNTIF function.

Syntax:

COUNTIF(range, criteria)

Example:
Suppose you have a list of names in cells A1:A10 and want to count how many times "John" appears:

=COUNTIF(A1:A10, "John")

This formula will return the number of times "John" appears in the range.

2. Counting All Duplicate Values in a Range

To count how many values are repeated at least once in a range, combine COUNTIF with SUMPRODUCT.

Formula:

=SUMPRODUCT(--(COUNTIF(A1:A10, A1:A10)>1))

Explanation:

1. COUNTIF(A1:A10, A1:A10) checks each value in the range against the entire range.

2. >1 identifies values that occur more than once.

3. -- converts the TRUE/FALSE results into 1s and 0s.

4. SUMPRODUCT adds all the 1s to give the total count of duplicate occurrences.

Note: This formula counts each duplicate occurrence, not unique duplicates. If a value appears three times, it counts all three.

3. Counting Unique Duplicate Values Only

To count unique duplicates (each repeated value counted once), use this formula with SUM and IF:

Formula (Array Formula in older Excel versions, press Ctrl+Shift+Enter): 

=SUM(IF(COUNTIF(A1:A10, A1:A10)>1, 1/COUNTIF(A1:A10, A1:A10), 0))

Explanation:

1. COUNTIF(A1:A10, A1:A10)>1 identifies duplicates.

2. 1/COUNTIF(A1:A10, A1:A10) ensures each duplicate is counted only once.

3. SUM adds up all the unique duplicates.

4. Alternative Using Pivot Table

1. Select your data range.

2. Go to Insert → PivotTable.

3. Drag the column with duplicates to Rows and Values.

4. Set Values to Count.

5. Filter values greater than 1 to see duplicates and their counts.

5. Conditional Formatting for Visual Identification

1. Select the range.

2. Go to Home → Conditional Formatting → Highlight Cells Rules → Duplicate Values.

3. Choose a format to highlight duplicates.

This method visually identifies duplicates and works well alongside formulas for counting.

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