Article ID: 214075 - Last Review: September 26, 2003 - Revision: 3.1

XL2000: How Chart Axis Limits Are Determined

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SUMMARY

This article explains how the automatic minimum and maximum limits for chart axis scales are computed in Microsoft Excel.

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MORE INFORMATION

In the following examples, the following names are used to describe certain values.

   Name   Description
   -------------------------------------------------------------------

   yMax   The maximum y value used in your chart.

   yMin   The minimum y value used in your chart.

   xMax   The maximum x value used in your chart. This applies only to
          charts that use x values, such as scatter and bubble charts.

   xMin   The minimum x value used in your chart. This applies only to
          charts that use x values, such as scatter and bubble charts.

When you create a chart in Microsoft Excel, there are three possible scenarios that can apply to your data:

Scenario one: the yMax and yMin values are both positive or equal to zero.
Scenario two: the yMax and yMin values are both negative or equal to zero.
Scenario three: the yMax value is positive, and the yMin value is negative.

The major unit used by the y-axis is automatically determined by Microsoft Excel, based on all of the data included in the chart. The following scenarios use this default major unit.

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Scenario 1

If the chart is a 2-D area, column, bar, line or x-y scatter chart, the automatic maximum for the y-axis is the first major unit greater than or equal to the value returned by the following equation:
yMax + 0.05 * ( yMax - yMin )
Otherwise, the automatic maximum for the y-axis is the first major unit greater than or equal to yMax.
If the difference between yMax and yMin is greater than 16.667 percent of the value of yMax, the automatic minimum for the y-axis is zero.
If the difference between yMax and yMin is less than 16.667 percent of the value of yMax, the automatic minimum for the y-axis is the first major unit less than or equal to the value returned by the following equation:
yMin - ( ( yMax - yMin ) / 2 )
Exception: If the chart is an x-y scatter or bubble chart, the automatic minimum for the y-axis is the first major unit less than or equal to yMin.

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Scenario 2

If the chart is a 2-D area, column, bar, line or x-y scatter chart, the automatic minimum for the y-axis is the first major unit less than or equal to the value returned by the following equation:
yMin + 0.05 * ( yMin - yMax )
Otherwise, the automatic minimum for the y-axis is the first major unit less than or equal to yMin.
If the difference between yMax and yMin is greater than 16.667 percent of the value of yMin, the automatic maximum for the y-axis is zero.
If the difference between yMax and yMin is less than 16.667 percent of the value of yMin, the automatic maximum for the y-axis is the first major unit greater than or equal to the value returned by the following equation:
yMax - ( ( yMin - yMax ) / 2 )
Exception: If the chart is an x-y scatter or bubble chart, the automatic maximum for the y-axis is the first major unit greater than or equal to yMax.

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Scenario 3

The automatic maximum for the y-axis is the first major unit greater than or equal to the value returned by the following equation:
yMax + 0.05 * ( yMax - yMin )
The automatic minimum for the y-axis is the first major unit less than or equal to the value returned by the following equation:
yMin + 0.05 * ( yMin - yMax )

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X-axis Limitations

The above information also applies to charts that use x values, such as x-y scatter charts and bubble charts. For these types of charts, substitute xMax and xMin for yMax and yMin in the above scenarios.

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