COMPLEX Function

The COMPLEX function returns the string representation of a complex number. For example:

=COMPLEX(4,3) // returns "4+3i"

To use the "j" instead of "i":

=COMPLEX(4,3,"j") // returns "4+3j"

To enter the value of a complex number without using the COMPLEX function, write it in a formula like this:

="4+3i"

Explanation

The Excel formula engine handles complex numbers as strings formatted like "x+yi" or "x+yj". For example, when we add two complex numbers together using the IMSUM function, the complex numbers are passed to the function as strings, and the result is a string representing the complex number that is the sum.

=IMSUM("4+3i","2-5i") // returns "6-2i"

We can perform the same operation using COMPLEX to get the strings representing the complex numbers.

=IMSUM(
    COMPLEX(4, 3),
    COMPLEX(2,-5)
) // returns "6-2i"

In general, The COMPLEX function is useful when you already have a complex number's real and imaginary values and want its string representation.

To read more about complex numbers in Excel, see this article.

Notes:

1. If omitted, the suffix defaults to "i".
2. The suffix must be lowercase "i" or "j"; other values result in a #VALUE error.
3. If real_num or i_num are non-numeric, COMPLEX returns the #VALUE! error