Add a Radius Constraint

1. Select Sketch | Constraints | Add radius constraint.
2. Select a circle or an arc.
3. Select the position of the dimension.
4. Edit the data in the Edit constraint dialog box.
5. Select OK.
6. Add more radius constraints by repeating steps 2-5 or finish adding radius constraints by pressing the ESC key or the middle mouse button.

Add a radius dimension to the axis of an ellipse by selecting a line either near the main axis of the ellipse or near the second axis, depending on to which axis you want to add the radius dimension.