If you are looking for **how to take ****log of negative numbers ****in Excel**, then you are in the right place. The logarithmic function is a basic function in mathematics. Frequent mathematical formulas use logarithmic functions. In Excel, it is easy to take a log of positive numbers. But there is no specific formula for but taking the log of negative numbers. In this article, weâ€™ll try to discuss how to take the log of negative numbers.

## How to Take Log of Negative Numbers in Excel: 3 Ways

Excel offers some combinations of functions and some easy ways to find the log of negative numbers. To show this we have made a dataset named **Data for Computer Simulation of a Project** which has column headers as **Check Point Number** and **Distance from Sea Level (m)**. The dataset is like this.

Letâ€™s see the ways to take the log of negative numbers.

### 1. Utilizing IF Function to Take Log of Negative Numbers

Initially, weâ€™ll see what happens to negative numbers when we use a normal **LOG function**.

- Firstly, write the following formula in the
**D5**cell like this.

`=LOG(C5)`

Here, **C5 **is the **Distance from Sea Level(m)** of **Check Point 1**.

- Secondly, press
**ENTER**to find the output as**3979**.

- Thirdly,
**use Fill Handle**by holding the mouse to the**right-bottom**corner of the reference**D5**cell and sliding the cursor downwards like the picture below to find other outputs from cells**D6**to**D15**.

Immediately, weâ€™ll get the output as shown in the following image.

More importantly, we can see that the outputs of the cells **D6, D9, D10, D12, **and **D15** are **#NUM!** Which means the output is invalid. This happens because the reference values of these output cells are negative, and the log of any negative number becomes a **complex number**. And **natural log function **makes **complex numbers** **invalid**.

Eventually, we can solve this issue by using an **IF function**. It is mainly a combination of **IF, ****COMPLEX****,** and** LOG **functions. This combined use of the functions gives an output of an **imaginary number** when we take a log of negative numbers.

To solve this issue, write the following formula in the **D5 **cell like this.

`=IF(C5<0,COMPLEX(LOG(ABS(C5)),PI()),LOG(C5))`

**Formula Breakdown**

**LOG(C5)**â†’ Returns**log**of**2.5****COMPLEX(LOG(ABS(C5))**â†’ Returns the absolute value if the**log(2.5)**is a complex number.**IF(C5<0,COMPLEX(LOG(ABS(C5)),PI()),LOG(C5))**â†’ Returns if the value of**C5**i.e. is less than**0**then**LOG(2.5)**is a complex number and**IF function**will return the absolute value of it. Otherwise, it will return normal positive value.

Secondly, press **ENTER** and use **Fill Handle** to find all the outputs like this.

Now, we can see that the log of negative numbers is no more **#NUM!**, rather they are shown as **imaginary numbers** as you can see **i**, the symbol of **imaginary numbers**, in the above output.

**Read More: How to Calculate Natural Logarithm in ExcelÂ **

### 2. Using IMLOG10 Function to Take Log of Negative Numbers

We can also simply use the **IMLOG10 ****function** to find the log values of negative numbers. It gives the same output as the usage of the **IF **function.

- Firstly, write the following formula in the
**D5**cell like this.

`=IMLOG10(C5)`

Here, **10** refers to the **base** of the **LOG **function.

- Secondly, press
**ENTER**and use**Fill Handle**to find the other outputs like this.

**Read More: How to Calculate Antilog in ExcelÂ **

### 3. Using Minimum Value to Find Comparative Log

We can also use the minimum value in a set of data to find a comparative log of negative numbers.

- Firstly, to find the minimum value among cells
**C5:C15**, select the cells and write the following formula in the**C17**

`=MIN(C5:C15)`

- Secondly, press
**ENTER**to get the output as**-7.6**.

Now, we need to take the positive value of that minimum value. Here it is **7.6**.

- Thirdly, in the
**C18**cell write the formula like this.

`=7.6+1`

Here, we want to take the value as **1** more than **7.6**. Thatâ€™s why we have added **1**.

- Fourthly, press
**ENTER**to find the output as**8.6**.

- Fifthly, we need to place that
**8.6**in the**D**Column. - Sixthly, write the following formula in the
**E5**cell to get the sum of**C5**and**D5**

`=D5+C5`

- Seventhly, press
**ENTER**to find the output as**11.1**and use**Fill Handle**to get all the outputs in the**E6:E16**columns.

Eventually, weâ€™ll see that all the values in **Column E**Â are positive although the values are different from those in **Column C**. Basically, the base values are changed, and weâ€™ll find the comparative log of the values.

- Eighthly, write the following formula in the
**F5**

`=LOG(E5)`

Here, **E5** is the sum of the cells** C5** and **D5**.

- Finally, press
**ENTER**and use**Fill Handle**to get all the outputs in the**F Column**like this.

**Read More: How to Calculate Logarithmic Growth in Excel**

## Things to Remember

- If we want to avoid complex numbers as the output of a log of negative numbers, we need to use the comparative log. Because this comparative log method brings the output without complex numbers.
- We can use the
**LN**function instead of the**LOG**function by simply inserting**LN**in the places of**LOG**in the formulas of**Method 1**and**Method 2**to get the**ln**

**Download Practice Workbook**

## Conclusion

We can find the log of any negative numbers if we study this article properly.

I have a question at point of positive of minimum value + 1, why the number 8.6 can become 8.9 ? that’s so confusing me.

Thanks a lot..

Dear

Gunawan,Thanks for your suggestions. We updated the article. You can check it now.

Regards

ExcelDemy