Interpolation is a process of determining the value of an unknown point that lies between two known data points. While calculating** linear interpolation** is an easy task in Excel, people often have to struggle when dealing with a non-linear dataset. Logarithmic graphs often convert a non-linear equation into a linear one, making it suitable to interpolate unknown values. In this article, we will show you two easy methods to calculate **logarithmic interpolation in Excel** effectively, with appropriate illustrations.

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## 2 Suitable Ways to Calculate Logarithmic Interpolation in Excel

In this article, we will demonstrate two suitable ways to calculate logarithmic interpolation in Excel. We will use the following dataset for this purpose.

### 1. Use Mathematical Formula to Calculate Logarithmic Interpolation in Excel

In this method, we will use a mathematical formula to calculate logarithmic interpolation in Excel. Follow these steps to learn how to do it.

__Steps:__

- First of all, letâ€™s assume,
**Depth of Flow**= X and**Discharge**= Y. - Then, insert two columns named
**LogX**and**LogY**. - After that, select cell
**D5**and write down the following formula.

`=LOG10(B5)`

- Similarly, select cell
**E5**and type the following formula.

`=LOG10(C5)`

- Hence,
**Autofill**the formula to the rest of columns**D**and**E**.

- Now we want to calculate the value of
**Discharge**for a**0.175m****Depth of Flow**. - To do so, select cell
**D12**and write down the following formula to determine**LogX**for**0.****175m****Depth of Flow**.

`=LOG10(B12)`

- Then select cell
**E12**and type the formula given below and hit**Enter**.

`=E7+((E8-E7)/(D8-D7))*(D12-D7)`

- After that, select cell
**C12**and write the following formula.

`=10^E12`

- Where
**E12**is the value of**LogY**. - Finally, press
**Enter**to get the interpolated**Discharge**value for**0.175m****Depth of Flow**.

**Read More: ****How to Perform Exponential Interpolation in Excel (4 Easy Ways)**

### 2. Utilize FORECAST Function to Calculate Logarithmic Interpolation in Excel

In this method, we will use** the FORECAST function** to determine logarithmic interpolation in Excel. Read the following steps to learn the procedure.

__Steps:__

- First, follow the same steps as the first method up to calculating
**LogX**for a**0.****175m****Depth of Flow**. - Then select cell
**E12**and write the following formula, given below.

`=FORECAST(D12,E5:E9,D5:D9)`

- After that, select cell
**C12**and type the following formula.

`=10^E12`

- Finally, hit
**Enter**and get the desired**Discharge**value for**0.****175m****Depth of Flow**.

__Notes__- These two methods give good results if the
**LogY vs LogX**graph is linear. - Donâ€™t forget to give proper
**cell references**or you wonâ€™t get the desired result.

**Read More: ****How to Interpolate in Excel Graph (6 Methods)**

## Conclusion

Thanks for making it this far. I hope you find this article useful. Now you know two methods **to calculate logarithmic interpolation in Excel**. Please let us know if you have any further queries, and feel free to give us any recommendations in the comment section below.

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