How to add a secondary axis in Excel

A secondary axis lets you plot two different data series on the same chart even when they use different scales — for example, monthly revenue in dollars alongside customer count in units. Excel calls this a "secondary vertical axis" when you add it to a column or line chart. The process takes three steps: create your chart with both data series, right-click the data series you want to move, and select the option to plot it on a secondary axis.

The secondary axis appears on the right side of your chart, with its own scale. This is useful when one series has much larger numbers than the other — if revenue ranges from $50,000 to $200,000 and customer count ranges from 100 to 500, plotting them on the same axis makes the smaller numbers invisible.

Key Takeaways

  • A secondary axis lets you display two data series with different scales on one chart, so neither series gets flattened visually.
  • You create the chart first with both data series included, then right-click the series you want to move and choose "Format Data Series".
  • The secondary axis appears on the right side of the chart and has its own scale independent of the left axis.
  • Column and line charts work best with secondary axes; pie and scatter charts do not support this feature.

Step-by-step: Creating a secondary axis

Start by selecting all the data you want to chart — both the labels and the two data series. Include the column headers so Excel knows what to label each series. Then go to the Insert tab and click Chart. Excel will open the chart wizard.

Choose a column chart or line chart (these are the only types that support a secondary axis). Excel will create a chart with both series plotted on the left axis. At this point, one series probably looks too small or too large compared to the other. Right-click directly on the bars or line of the series you want to move — not on the chart background, but on the actual data points. A menu will appear. Click "Format Data Series".

In the Format Data Series panel that opens on the right side of your screen, look for the "Series Options" section. You will see a radio button or toggle for "Secondary Axis". Click it. The selected series will jump to the right side of the chart, and a new axis scale will appear on the right edge. Both axes now have their own scales, so both series are visible and readable.

When a secondary axis makes sense

Use a secondary axis when you are comparing two things measured in different units or with very different ranges. Common examples include revenue versus customer count, temperature versus humidity, or website traffic versus conversion rate. The secondary axis prevents one series from being visually dominated by the other.

Do not use a secondary axis if both series use the same unit and similar ranges — it makes the chart harder to read without adding clarity. If you have more than two series, a secondary axis becomes confusing; consider using separate charts instead.

Formatting the secondary axis

Once the secondary axis exists, you can format it the same way you format the primary axis. Right-click on the numbers on the right side of the chart (the secondary axis itself) and select "Format Axis". You can change the minimum and maximum values, the number format, the font size, and the label text.

You can also add a title to the secondary axis to label what it measures. Right-click the axis title area on the right side and select "Edit Axis Title", then type a label like "Customer Count" or "Units Sold". This helps anyone reading the chart understand what the right-side numbers represent.

Common problems and fixes

If you right-click and do not see "Format Data Series", you clicked the wrong element. Make sure you are clicking directly on the bars or line of the data series itself, not on the chart background or the axis. The cursor should change to show a small chart icon when you hover over the correct spot.

If the secondary axis option is grayed out or missing, you are using a chart type that does not support it — pie charts, doughnut charts, and scatter plots cannot have secondary axes. Switch to a column or line chart instead. If you have already created the chart and want to change its type, right-click the chart and select "Change Chart Type".

If both series still look visually unbalanced after adding the secondary axis, adjust the axis scales manually. Right-click the axis that looks wrong and select "Format Axis". Change the maximum value to make the scale taller or shorter until both series are equally visible.

Secondary axis versus separate charts

A secondary axis works well for comparing two related series side by side. If you need to compare more than two series, or if the series are unrelated, two separate charts often communicate better. A secondary axis can confuse readers because the two axes use different scales — someone might misinterpret the visual height of the bars as a direct comparison.

If you choose to use separate charts instead, place them one above the other or side by side so readers can see both at once. Label each chart clearly with its own title and axis labels. This approach takes more space but is clearer when the data series are very different or when you have more than two series to show.

Frequently Asked Questions

Can I add a secondary axis to a pie chart?

No. Pie charts do not support secondary axes because they do not use a coordinate system with axes. Only column charts, line charts, area charts, and bar charts support secondary axes. If you need to compare two data series and one is a percentage or proportion, use a column or line chart instead.

What if I want to move the secondary axis to the left instead of the right?

Excel does not offer an option to move the secondary axis to the left side. The secondary axis always appears on the right. If you need both axes on the left, you would need to use a different tool or create two separate charts.

Can I have more than one secondary axis?

No. Excel allows only one primary axis and one secondary axis per chart. If you have three or more data series with different scales, create separate charts for each pair or group of related series.

How do I remove a secondary axis after I add it?

Right-click the data series on the secondary axis and select "Format Data Series". In the Series Options section, click the radio button for "Primary Axis" to move the series back. The secondary axis will disappear if no series are using it.

Does the secondary axis work in Excel on Mac?

Yes. The steps are the same on Mac Excel as on Windows Excel. Right-click (or Control-click) the data series, select "Format Data Series", and toggle the secondary axis option in the panel that appears.