It can be very helpful to know how to add multiple data series to an Excel chart. However, when dealing with data in different units, you may find it challenging to create the chart you need. Don't worry, not only can you do it, but it's also quite easy!
Steps
Add a second Y-axis

Create a chart in Excel, assuming all data shares the same unit.

Access the chart and right-click on the data series line that you want to add a second Y-axis for. In this example, if you want to add a Y-axis for percentage values, right-click the red line.

Select "Format Data Series" from the options.

Under the "Axis" section, choose the radio button next to "Secondary Axis".

Click OK, and you will see the second Y-axis appear on your chart.
Change the chart type for the second data series

Return to the chart and right-click on the data series line that you wish to add a second Y-axis for. In this example, if you want to add a Y-axis for percentage values, right-click the red line.

Select "Change Series Chart Type" to modify the chart type.

Choose the chart type that you want to apply to the second data series. In this case, it is a column chart.
Tip:
- You can create three or more Y-axes in Excel using EZplot or Multy_Y from OfficeExpander.com. Use the trial version to ensure it fits your needs.
- Practice on simple data sets first to become more proficient.
