But the measure tool will tell you the circumference.
Maybe through creating a few equations.
Will the major and minor axis always be in the same ratio? you can have the same approximate circumference with an infinite number of ellipses.
I want to control the size of an ellipse in my sketch by the circumference.
This could be achieved using equations or a DT. However, the accuracy of the result will depend upon the formula used.
See http://www.mathsisfun.com/geometry/ellipse-perimeter.html for more details.
The DT could propagate the result to a custom property in the model.
Is there a way to dimension the circumference?
No, but a note linking the custom property created by the DT, could be attached to the drawing view.
Interesting question. Modern mathematics has not yet devised a formula to calculate the perimeter of an ellipse from its size parameters. SW will measure, but it will be an approximation.