An ellipse -- or oval -- is a closed curve that resembles an elongated circle. The length of an ellipse is the length of the longer axis, called the major axis. The width of an ellipse is the length of the shorter axis, called the minor axis. The two fixed points are called foci (plural of focus). The foci of an ellipse always lie on the major axis. Knowing how to draw a perfect ellipse can come in handy for cutting oval mirrors, tiles, or any home project where you need an elliptical shape.
Draw the axes of the ellipse as a cross on the surface on which you wish to create an ellipse. The two axes should cross in the middle. For example, if you want to draw an ellipse that is 34 inches long and 16 inches wide, use your ruler to draw perpendicular lines measuring those lengths.
Square the lengths of both axes, and find the difference between the two values. For example, 34^2 = 1156, 16^2 = 256, and 1156 - 256 = 900.
Then, take the square root of your answer. The square root of 900 is 30.
Lastly, divide that answer by 2. So, 30/2 = 15. This means that each focus is 15 inches from the center of where the axes intersect along the major axis (the longer axis).
Draw two points along the major axis 15 inches from the center in each direction. Put your thumbtacks or nails at the end of the sides of the major axis
Cut out the correct length of string. When constructing an ellipse, the length of the string always equals the length of the major axis. Using the example above, you would need 34 inches of string.
Tie your string to the thumbtacks or nails, ensuring the string is taut.
Pull the thumbtacks or nails out, and put them into the foci points along the major axis that you drew earlier.
Put the point of your pencil along the string and pull the string with the tip.
Keep the string taut and move the pencil in an arc to draw your ellipse. Draw each the two arcs separately to avoid hitting the nail or thumbtack.