Dimensioning Ellipses

From the Sketch section of the action bar, click Sketch Dimension

.

Select and drag an elliptical curve to add a dimension for the major axis.

Alternatively, select and drag the major axis.

Select the center point and the curve to add a dimension to the minor axis.

Alternatively, select and drag the minor axis.

Alternatively, right-click the curve and from the context toolbar menu, click Major Radius or Minor Radius to add a dimension to major and minor axes.