Author: Oscar Cronquist Article last updated on November 19, 2018

Formula in C12:

=SUM(1/COUNTIF($B$3:$B$8, $B$3:$B$8))+SUM(IF(COUNTIF($B$3:$B$8, $D$3:$D$8)=0, 1/COUNTIF($D$3:$D$8, $D$3:$D$8), 0))

How to create an array formula

  1. Double press with left mouse button on cell C12
  2. Paste above formula
  3. Press and hold Ctrl + Shift
  4. Press Enter

Explaining formula in cell C12

Step 1 - Count values in cell range B3:B8

The COUNTIF function counts values equal to a condition or criteria.

COUNTIF($B$3:$B$8, $B$3:$B$8)

becomes

COUNTIF({"AA";"BB";"AA";"CC";"BB";"AA"}, {"AA";"BB";"AA";"CC";"BB";"AA"})

and returns

{3;2;3;1;2;3}

Step 2 - Divide 1 with array

1/COUNTIF($B$3:$B$8, $B$3:$B$8)

becomes

1/{3;2;3;1;2;3}

and returns

{0.333333333333333;0.5;0.333333333333333;1;0.5;0.333333333333333}

Step 3 - Sum values

The SUM function simply adds the numbers and returns the total.

SUM(1/COUNTIF($B$3:$B$8, $B$3:$B$8))

becomes

SUM({0.333333333333333;0.5;0.333333333333333;1;0.5;0.333333333333333})

and returns 3.

Step 4 - Which values exist in cell range $D$3:$D$8

COUNTIF($B$3:$B$8, $D$3:$D$8)=0

becomes

COUNTIF({"AA";"BB";"AA";"CC";"BB";"AA"}, {"BB";"CC";"DD";"CC";"BB";"BB"})=0

becomes

{2;1;0;1;2;2}=0

and returns

{FALSE; FALSE; TRUE; FALSE; FALSE; FALSE}

Step 5 - Convert TRUE to corresponding number

The IF function uses a logical expression (argument1) to determine which value to return (TRUE - argument2 , FALSE - argument3)

IF(COUNTIF($B$3:$B$8, $D$3:$D$8)=0, 1/COUNTIF($D$3:$D$8, $D$3:$D$8), 0)

becomes

IF({FALSE; FALSE; TRUE; FALSE; FALSE; FALSE}, 1/COUNTIF($D$3:$D$8, $D$3:$D$8), 0)

becomes

IF({FALSE; FALSE; TRUE; FALSE; FALSE; FALSE}, {0.333333333333333;0.5;1;0.5;0.333333333333333;0.333333333333333}, 0)

and returns

{0;0;1;0;0;0}.

Step 6 - Sum array

SUM(IF(COUNTIF($B$3:$B$8, $D$3:$D$8)=0, 1/COUNTIF($D$3:$D$8, $D$3:$D$8), 0))

becomes

SUM({0;0;1;0;0;0})

and returns 1.

Step 7 - Add numbers

SUM(1/COUNTIF($B$3:$B$8, $B$3:$B$8))+SUM(IF(COUNTIF($B$3:$B$8, $D$3:$D$8)=0, 1/COUNTIF($D$3:$D$8, $D$3:$D$8), 0))

becomes

3+SUM(IF(COUNTIF($B$3:$B$8, $D$3:$D$8)=0, 1/COUNTIF($D$3:$D$8, $D$3:$D$8), 0))

becomes

3+1

and returns 4 in cell D12.

Get Excel *.xlsx file

Count unique distinct values in two columns.xlsx

Weekly Blog EMAIL

Welcome! I am Oscar and here to help you out.

Feel free to comment and ask Excel questions.

Make sure you subscribe to my newsletter so you don't miss new blog articles.

Related articles

Count unique distinct months

The formula in cell D18 counts unique distinct months in cell range B3:B16. Formula in D18: =SUMPRODUCT((FREQUENCY(DATE(YEAR($B$3:$B$16), MONTH($B$3:$B$16), 1), DATE(YEAR($B$3:$B$16), […]