When you make a chart, Excel determines the scale of the Y-axis based on the numbers in your data set.  If the range of your data (the difference between the highest and lowest numbers) is greater than 20% of the lowest number in your data set, then the Y-axis of your chart will go from zero to a number greater than the highest number in your chart. If the range of your data is less than 20% of the lowest number, then the Y-axis will not start at zero, but at a number slightly lower than the lowest number in your data set, like in the first chart at the top of this post.

In the two charts above, the first one uses the scale Excel assigned to it using the 20% rule.  It illustrates the fluctuation in temperature over the course of the week (this is Austin’s forecast for the week).

But sometimes you may not want the default scale and will need to change it. In the second chart, I adjusted the Y-axis so it starts at zero.  Now it doesn’t emphasize the fluctuation in temperatures, but it does show how far the nineties are from zero, and that this week is rather hot*. 

You always have the option to change the scale of your chart to meet your needs.

Change the Y-Axis Scale

  1. Select your chart.
  2. On the Layout tab of the ribbon, click on the Axes button.
  3. Select Primary Vertical Axis.
  4. Select More Vertical Axis Options.
  5. In the Axis Options section, for Minimum, select Fixed and enter the lowest number you want on your Y-axis.
  6. For Maximum, select Fixed, and type the number where you want the Y-axis to end.
  7. Click Close.

Note: if you’ve already changed your axis and want to go back to Excel’s defaults, select Auto, instead of Fixed and click Close.

*  I realize that for some readers living in other parts of the world, the nineties are practically chilly.  I hope you’re reading this with an iced beverage and a fan. Or air conditioning.

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Try a Logarithmic Axis