This article explains how to add a secondary axis to a chart in Excel so that you can view different things in the same chart. These instructions work in Excel in Microsoft 365, Excel 2019, Excel 2016, and Excel 2013.
How to Add or Remove a Secondary Axis in Microsoft Excel
Excel charts allow you to visualize your data in a variety of ways. Charts that use an X and Y axis format allow you to view a range of data, allowing you to compare two different things, but those things usually have the same unit of measurement. A secondary axis is used to compare two things that do not have the same unit of measurement.
First, select the row (or column) associated with the second data series.
When you select an element in a chart, the Chart Tools tab appears on the ribbon.