This article explains how to add a secondary axis to a chart in Excel so you can view unlike categories on the same graph. These instructions work in Excel in Microsoft 365, Excel 2021, Excel 2019 ...

Adding a Second Y-Axis Your new series may not be measured with the same range of numbers as the old one. To make the chart look better, you can plot the new series on a differently scaled y-axis.

Adding Data Sets One at a Time Launch Excel and load the spreadsheet containing the data you want to plot. Select the first set of X and Y axis data for your chart.