HasAutoAspectRatio Property
False if the aspect ratio of the specified chart has been modified. Set this property to True to restore the specified chart to it's default aspect ratio. Read-write Boolean.
expression.HasAutoAspectRatio
expression Required. An expression that returns a ChChart object.
Example
This example resets the first chart in Chartspace1 to its default aspect ratio.
Chartspace1.Charts(0).HasAutoAspectRatio = True