Suppose we have a row contains some value, such as A, B, C, D, E, and a row contains some value, such as F, G, A, B, E, I. Two columns have common set: A, B, E. In Excel we can count size of common set by using a formula that combines the COUNTIF and SUMPRODUCT functions.

**The general formula**: `=SUMPRODUCT(COUNTIF(range1,range2))`

‘**range1**‘ and ‘**range2**‘ are range of cells

**Example:**

A | B | |

1 | A | E |

2 | B | I |

3 | C | A |

4 | D | B |

5 | E | |

6 | F | |

7 | G |

**Formula:** `=SUMPRODUCT(COUNTIF(A1:A7,B1:B4))`

The result is: **3**