If you are on an older version of Excel, use the INDEX/MATCH method described below. If you are a Microsoft 365 subscriber, or are using Excel 2021, Excel for the web, or Excel for iOS or Android devices, you can use the XLOOKUP function to extract the values. However, if you need even greater accuracy, you may want to consider a more advanced method such as cubic splines.
In most cases linear interpolation in Excel will provide results that are sufficiently accurate. Linear interpolation assumes that the change in y for a given change in x is linear. To interpolate between x- and y-values in a large data set (more than 2 pairs of values), use either XLOOKUP or INDEX and MATCH to extract a pair of x- and y-values to interpolate between.
