To Dimension an Elliptic Fillet or Ellipse
The horizontal and vertical endpoints of the ellipse and its center point can be dimensioned as regular Sketcher points. You can also dimension the x- and y-radii of the elliptical fillet.
1. Click > 
Normal or right-click and choose Dimension from the shortcut menu.
Normal or right-click and choose Dimension from the shortcut menu.2. Click the fillet or ellipse (do not pick endpoints).
3. Click the middle mouse button to place the dimension.
4. Select one of the following from the Ellipse Rad dialog box:
◦ Major Axis
◦ Minor Axis