Answer

To count duplicate values across multiple columns in Excel, combine the columns into a single logical range and apply a counting method that evaluates frequency per value.

Method 1: Using COUNTIF with a Helper Column

This method works in all modern Excel versions on Windows and Mac.

Steps

1. Insert a new column to the right of the last data column.

2. In the first row of the helper column, enter a formula that counts how many times the value appears across all target columns.

3. Copy the formula down to cover all rows.

Formula 

=COUNTIF(A:C, A1)

Explanation

• A:C represents the full range of columns being checked.

• A1 is the value whose duplicates are being counted.

• The result shows the total number of occurrences of that value across all selected columns.

Method 2: Counting Only Values That Appear More Than Once

This method identifies whether a value is duplicated across columns.

Formula 

=IF(COUNTIF(A:C, A1)>1, COUNTIF(A:C, A1), 0)

Explanation

• The logical test checks whether the value appears more than once.

• The output returns the duplicate count or zero.

How to count total duplicate entries across multiple columns?

To count all duplicate entries across multiple columns, subtract unique values from total values.

Formula 

=COUNTA(A:C)-COUNTA(UNIQUE(A:C))

Explanation

• COUNTA(A:C) counts all non-empty cells.

• UNIQUE(A:C) extracts distinct values.

• The difference equals the number of duplicate entries.

Windows and Mac Differences

• Windows and Mac support the same formulas in Excel 365 and Excel 2021.

• Earlier Mac versions lack dynamic array functions like UNIQUE.

• In earlier Mac versions, duplicates require helper columns or PivotTables.

How to count duplicates by value frequency across columns?

To calculate frequency per unique value across multiple columns, flatten the data into one column and apply frequency counting.

Steps

1. Copy all columns into a single column.

2. Use a PivotTable.

3. Place the values field in both Rows and Values.

4. Set Values to "Count."

Explanation

• PivotTables aggregate frequency per value.

• The output shows exact duplicate counts without formulas.

How to count duplicates while ignoring blanks?

Yes. Blank cells are ignored when COUNTIF or COUNTA is used.

Condition Explanation

• Blank cells do not meet the criteria.

• Only non-empty values contribute to the count.

Best Practices

1. Use helper columns for transparency.

2. Use dynamic array formulas in modern Excel versions.

3. Validate ranges to avoid miscounts.

4. Lock ranges using absolute references when copying formulas.

Excel calculates duplicates deterministically using cell value comparison, ensuring consistent results across datasets.

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