How to Interpolate in Excel Graph (6 Methods)

In Excel, interpolation allows us to determine the value between two points on a graph or curve. It helps us anticipate future values that lie between existing data points. Let’s explore six methods for interpolation in an Excel graph.

Method 1 – Mathematical Equation for Linear Interpolation

Steps

• Start by creating a chart from your dataset (Go to INSERT > Scatter).

• Add a trendline to the graph (assuming linear growth data).

• Select the x-values (x1 and x2) and corresponding y-values (y1 and y2) around the desired point (e.g., week 8).

• Enter the following formula in cell F13 to interpolate the value for week 8:

• Press ENTER.

• Right-click on the graph, choose Select Data.

• Click Add from the popped-up dialogue box.

• Add the interpolated value. Select the X and Y cells.

• Click OK.

Method 2 – Interpolation Using Trendline

Steps

• Add a trendline to the graph (similar to Method 1).
• Right-click the trendline, select Format Trendline, and enable Display Equation on Chart.

• The equation displayed represents the interpolated linear relationship.

• Calculate the interpolated value for week 8 using the equation.
• Enter the following formula in F7:

• Press ENTER.

• Follow Method 1, to add interpolate data in the graph.

Method 3 – Interpolation Using SLOPE and INTERCEPT Functions

Steps

• Insert a graph and add a trendline (as in Method 1).
• In cell F7, enter the following formula:

• Press ENTER to calculate the interpolated value.

• Herewith the final graph chart, after adding the interpolate value.

• Follow Method 1, for adding interpolate values in an Excel chart.

Method 4 – Using FORECAST Function

Steps

• Create a chart and add a trendline (similar to Method 1).
• In cell F7, enter the following formula:

• Press ENTER to obtain the interpolated value.

• Herewith the final graph chart, after adding the interpolate value.

Method 5 – Interpolation Using TREND Function

Steps

• Add a chart and trendline as in Method 1.
• In cell F7, enter the following formula:

• Press ENTER to calculate the interpolated value.

Finally, add the interpolation value in the chart as we did earlier in Method 1.

Method 6 – Interpolation Using GROWTH Functions

Steps

• Insert a chart and add an exponential trendline (similar to Method 1).
• In cell F7, enter the following formula:

• Press ENTER to find the interpolated value.

• Add the interpolation value in the chart.

Read More: How to Do Interpolation with GROWTH & TREND Functions in Excel

Practice Section

We’ve attached a practice workbook so that you can practice these methods.

Download Practice Workbook

You can download the practice workbook from here:

Related Articles

• How to Interpolate Missing Data in Excel
• How to Do Linear Interpolation in Excel
• How to Do VLOOKUP and Interpolate in Excel
• How to Interpolate Between Two Values in Excel
• How to Perform Bilinear Interpolation in Excel
• How to Use Non Linear Interpolation in Excel
• How to Do Linear Interpolation Excel VBA

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