Data interpolation is a very important thing when we analyze an experiment, or we want to predict or determine the results of an event. For instance, if we have data on two different occasions, we can determine the data between those occasions by interpolation. This article will briefly describe 6 methods for how to interpolate between two values in Excel. In the dataset, we have some X Coordinates and Y Coordinates.

**1. Using FORECAST/FORECAST.LINEAR Function to Interpolate Between Two Values in Excel**

The simplest way to interpolate between two values is to use the **FORECAST/FORECAST.LINEAR** function. Let’s go through the description below.

**Steps:**

- Determine which value you want to interpolate and make new rows for the value you want to interpolate and the interpolated In this case I want to interpolate between 8 and 9 so I chose a value of 8.5.

- Now, type the following formula in cell
**B15**.

`=FORECAST(C14,C5:C12,B5:B12)`

Here, the **FORECAST **function determines the interpolated value in cell **C15 **via linear regression. It works on the ranges** B5:B12 **(as **known_Xs**) and **C5:C12 **(as **known_Ys**).

- Hit the
**ENTER**button, and you will see the interpolated value in cell**C15**.

- You can also use the
**LINEAR**function in this case. Just put**FORECAST.LINEAR**instead of**FORECAST**in the formula.

`=FORECAST.LINEAR(C14,C5:C12,B5:B12)`

- Hit
**ENTER**and you will see the same interpolated value as before.

Thus, you can easily interpolate between two values using the **FORECAST **function.

**2. Combining Excel XLOOKUP and FORECAST Functions to Interpolate Between Two Values**

If you want to interpolate within a small range of the dataset, you can use **the XLOOKUP function** to extract the coordinates in the range and interpolate a value within them. Suppose we want to interpolate the value 6 in **B9:C10**. Let’s discuss the procedure below.

**Steps:**

- First, make some modifications to the dataset to place the coordinates.

- Type the following formula in cell
**F7**.

`=XLOOKUP(C14, B5:B12,B5:B12,,-1,1)`

The **XLOOKUP **function looks up the value in **C14**, searches for this value in the range** B5:B12, **and returns the value which is adjacently smaller than **6.5** as it cannot find this exact value in that range and we put **-1 **in this regard. Thus we get **x1 **as **5**.

A similar formula is used several times in this section. When we need a value adjacently larger than **6.5**, we used ‘**1**’ instead of ‘**-1**’ in the formula.

- Hit
**ENTER**to see the result in cell**F7**.

- Now, type the following formula in cell
**F8**.

`=XLOOKUP(C14, B5:B12,B5:B12,,1,1)`

- Hit the
**ENTER**key, and you will see a larger value than 6 in cell**F8**.

- After that, type the following formula in cell
**F9**.

`=XLOOKUP(C14, B5:B12,C5:C12,,-1,1)`

- Hit
**ENTER**. This operation will deliver you the value in cell**C9**.

- Then, type the formula in cell
**F10**.

`=XLOOKUP(C14, B5:B12,C5:C12,,1,1)`

- Hit
**ENTER**, and you will see the**Y Coordinate**of cell**C10**.

- After that, select cell
**C15**and type the formula given below.

`=FORECAST(C14,F9:F10,F7:F8)`

- Press the
**ENTER**key to see the interpolated value in cell**C15**.

Thus, you can interpolate between two values within a small range.

**3. Inserting INDEX- MATCH with FORECAST Function to Interpolate Between two Values**

We can also interpolate between two values within a small range of the dataset by using the **INDEX** and **MATCH** functions to extract the coordinates in the range and interpolate a value within them. Suppose we want to interpolate the value 6 in **B9:C10**. Let’s discuss the procedure below.

**Steps:**

- First, make some modifications in the dataset to place the coordinates.

- Type the following formula in cell
**F7**.

`=INDEX(B5:B12,MATCH(C14,B5:B12,1))`

Here, the **MATCH **function returns the position of the cell value of **C14 **in the range** B5:B12**. And then the **INDEX **function returns the value of that position in **B5:B12**. Thus, it returned **x1**.** **

A similar formula is used in this section several times to determine **x2**,** y1, **and **y2**.

- Hit
**ENTER**to see the result in cell**F7**.

- Now, type the following formula in cell
**F8**.

`=INDEX(B5:B12,MATCH(C14,B5:B12,1)+1)`

- Hit the
**ENTER**key, and you will see a larger value than 6 in cell**F8**.

- After that, type the following formula in cell
**F9**.

`=INDEX(C5:C12,MATCH(C14,B5:B12,1))`

- Hit
**ENTER**. This operation will deliver you the value in cell**C9**.

- Then, type the formula in cell
**F10**.

`=INDEX(C5:C12,MATCH(C14,B5:B12,1)+1)`

- Hit
**ENTER**, and you will see the**Y Coordinate**of cell**C10**.

- After that, select cell
**C15**and type the formula given below.

`=FORECAST(C14,F9:F10,F7:F8)`

- Press the
**ENTER**key to see the interpolated value in cell**C15**.

Thus, you can interpolate between two values within a small range.

**4. Interpolating Between Two Values by Applying Mathematical Formula **

Another effective method to interpolate between two values will be to apply a mathematical formula. The interpolation formula is given below.

This is an equation of a straight line. Let’s follow the necessary instructions to apply it to interpolate between two values.

**Steps:**

- Make some modifications in the dataset for interpolation value and type the following formula in cell
**C15**. Here, we want to find the interpolated value when the**X Coordinate**is 75. For this reason, we are going to take**X Coordinates**which are adjacently smaller or greater than 2.75, and their corresponding**Y Coordinates**in this dataset.

`=C7+(C14-B7)*(C8-C7)/(B8-B7)`

The formula returns the interpolated value by measuring the slope of the 2 points which are **(2.5, 4) **and **(3, 6)**.

- Now, just hit
**ENTER**to see the interpolated value in cell**C15**.

Thus, you can interpolate between two values just by using a mathematical equation.

**Read More: **How to Interpolate in Excel Graph

**5. Interpolating between Two Values by Joining SLOPE and INTERCEPT Functions**

One of the easiest ways to interpolate between two values is to use Excel **SLOPE** and **INTERCEPT** functions and use their results into a straight-line formula. Let’s see the procedure below. We want to interpolate the **X Coordinate **10.

**Steps:**

- Make some changes in your dataset to store the slope.

- Type the following formula in cell
**E7**

`=SLOPE(C5:C12,B5:B12)`

The **SLOPE **function returns the slope/gradient of the linear regression line which is made by the points formed by given **X **and **Y **Coordinates.

- Hit
**ENTER**, and you will see the slope of these data in cell**E7**.

- Now, type the following formula in cell
**E9**to find the**Y-intercept**.

`=INTERCEPT(C5:C12,B5:B12)`

The **INTERCEPT **function returns the **Y-intercept **of the linear regression line which is made by the points formed by given **X **and **Y Coordinates**.

- Hit
**ENTER**to see the output in cell**E9**.

- Insert this formula in cell
**C15**.

`=E7*C14+E9`

The formula is a basic straight-line formula, which is **y=mx+c**.

- Hit
**ENTER**to see the interpolated value in cell**C15**.

Thus, you can determine the interpolated value between two values by using Excel **SLOPE **and **INTERCEPT **functions.

**Read More: **How to Interpolate Missing Data in Excel

**6. Using Excel GROWTH Function for Nonlinear Interpolation**

**The GROWTH function** is a special function to interpolate non-linear data. Our dataset basically consists of non-linear relations between **Y **and **X Coordinates**. So, it would be best to use this function.

**Steps: **

- Make some changes to store the interpolated. We want to interpolate a value between 5 and 8. Let it be 6.5.

- Type the following formula in cell
**C15**.

`=GROWTH(C5:C12,B5:B12,C14)`

Here, the **GROWTH **function returns the interpolated data by predicting the exponential growth of the **X **and **Y Coordinates**.

- Hit
**ENTER**, and you will see the interpolated value in cell**C15**.

Thus, you can find interpolated values by using the **GROWTH **function. As this function works for non-linear relations, you can have more accurate data as a result of its help.

**Download Practice Workbook**

## Conclusion

The bottom line is that this article will help you understand how to interpolate between two values in Excel. By interpolation, you can determine the exact or most accurate result for data that is not included in an experiment, which is really important in scientific and statistical affairs. If you have any better methods of interpolating between two values in Excel, please leave them in the comment box. And also, share your feedback on my article. This will help me enrich my upcoming articles.

## Related Articles

- How to Do Interpolation with GROWTH & TREND Functions in Excel
- How to Do Linear Interpolation in Excel
- How to Perform Bilinear Interpolation in Excel
- How to Use Non-Linear Interpolation in Excel
- How to Do VLOOKUP and Interpolate in Excel
- How to Do Linear Interpolation Excel VBA

**<< Go Back to Excel Interpolation | Excel for Statistics | Learn Excel**