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 ...

How Excel Charts Work A chart has an x-axis range and a y-axis range to show the correlation between two different data sets. The x-axis is the horizontal category line.

Excel automatically distributes these points along a uniform X axis. To add more data to the Y axis in a line chart, add additional numbers in cells below your existing data.