Question: how do you find the length and width of an ellipse?
Answer: 2 Answers. The width of an ellipse is twice its semi-minor axis, b, and the length is twice its semi-major axis, a. The distance from the focus, F, to the end of the semi-minor axis, B, is the same as the distance from the center of the ellipse, O, to the end of the semi-major axis, A.