In this tutorial, you will learn how to use linear interpolation in Excel.

A technique for fitting curves with linear polynomials is linear interpolation. It facilitates the construction of new data points within the bounds of a discrete collection of existing data points. Consequently, the simplest method for estimating a channel from the vector of estimates for the given channel is linear interpolation. It is particularly helpful for a variety of mathematical and scientific applications, including market research, data forecasting, and data prediction.

Once ready, we’ll get started by utilizing real-world examples to show you how to use linear interpolation in Excel.

Table of Contents

## Anatomy of Linear Interpolation

There are two primary methods for using linear interpolation in Excel. The first method involves putting the linear interpolation mathematical formula into a calculator. This equation is:

y = y1 + (x – x1) â¨¯ (y2 – y1) / (x2 – x1)

X1, X2, Y1, and Y2 are all known values in this equation. You can determine the alternative coordinate for a given value by substituting a new value for either y or x.

Using the FORECAST function, which in Excel is defined as =FORECAST(x,known ys,known xs), is the second method for performing linear interpolation. These are the components of this function:

known ys: All of the known values for y are represented by this variable. You would enter the cell coordinates for every value for y, for instance, if your chart had 10 different x and y values.

known xs: variable is identical to the known ys field but represents all x values. Similar to the y coordinates, you must enter every known value of x while filling out this variable.

x: The value you’re looking for is represented by the variable x in this function. A linear interpolated y value is produced when a number is inserted for the x variable.

## Use Linear Interpolation in Excel

Before we begin we will need a group of data to use linear interpolation in Excel.

### Step 1

First, you need to have a clean and tidy group of data.

### Step 2

For example, if you want to look for the y value for a new x value which is 20, you can use this formula =FORECAST(20,OFFSET(B2:B8,MATCH(20,A2:A8,1)-1,0,2), OFFSET(A2:A8,MATCH(20,A2:A8,1)-1,0,2)).

### Step 3

Once you press Enter, your formula will return the y value for the new x value inputted by using interpolation.