# A to Z of Excel Functions: The COMPLEX Function

15 September 2017

*Welcome back to our regular A to Z of Excel Functions blog. Today we look at the COMPLEX function. *

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**The COMPLEX function**

Imagine this complex function. This function converts real and imaginary coefficients into a complex number of the form **x + yi** or **x + yj**, where **i** or **j **denotes the square root of -1.

The COMPLEX function employs the following syntax to operate:

**COMPLEX(real_num, i_num, [suffix])**

The **COMPLEX** function has the following arguments:

**real_num:**this is required and represents the real coefficient of the complex number**i_num:**this is also required. This denotes the imaginary coefficient of the complex number**suffix:**this argument is optional. The suffix for the imaginary component of the complex number. If omitted,**suffix**is assumed to be "**i**".

**NOTE:** All complex number functions accept "**i**" and "**j**" for **suffix**, but neither "I" nor "J". Using uppercase results in the #VALUE! error value, given the possible confusion with cell references *etc*. All functions that accept two or more complex numbers require that all suffices match.

It should be further noted that:

- if
**real_num**is non-numeric,**COMPLEX**returns the*#VALUE!*error value - if
**i_num**is non-numeric,**COMPLEX**returns the*#VALUE!*error value - if
**suffix**is neither "**i**" nor "**j**",**COMPLEX**returns the*#VALUE!*error value - arithmetic operations involving imaginary numbers require specific functions such as
**IMSUB**(subtract),**IMSUM**(add),**IMPRODUCT**(multiply) and**IMDIV**(divide). If these are not used, the calculations will return the*#VALUE!*error value.

Please see my example below:

*We’ll continue our A to Z of Excel Functions soon. Keep checking back – there’s a new blog post every other business day.*

*A full page of the function articles can be found here. *