The double minus, also known as double *unary*, is an operation to convert Boolean values into ones and zeroes. Simply; TRUE to one (1) and FALSE to zero (0).

The double minus operator is useful when working with arrays. The most common use case is to combine a double minus operator with SUMPRODUCT function. The **SUMPRODUCT** function can work with arrays without array formulas. As a result, you can bypass the limitations of Excel's conditional functions like SUMIF and SUMIFS.

Let's analyze how the double minus acts, step by step:

=SUMPRODUCT(--($B$3:$B$12=D4))

$B$3:$B$12 range refers to an array of values between B3 and B12 cells

*{2018;2018;2018;2018;2018;2018;2018;2019;2019;2019}*

$B$3:$B$12=D4 operation compares the values of the array with the value of the cell D4, "2019". This action returns another array which contains the Boolean values. *TRUE* for matched values and *FALSE* otherwise.

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

The double minus converts Boolean values to ones and zeroes. So --($B$3:$B$12=D4) operation returns an array of ones and zeroes. It mean that ones represents the match and zeroes others.

*{0;0;0;0;0;0;0;1;1;1}*

Finally; the **SUMPRODUCT** sums the contents of the final array to return the number of matched values.

*3*

Alternatively; you can use the **N** function to convert Boolean values into ones and zeroes. It simply returns a value converted to a number which means TRUE to 1 and FALSE to 0.