An oval is a shape that resembles an egg; in fact, the word "oval" comes from the Latin word "ovum," meaning egg. In mathematics, there is no generally agreed upon definition of an oval, so it is difficult to find the length of any oval shape. However, ovals closely resembles ellipses, and it is possible to find the total length around an ellipse in a straightforward manner, which offers a very good approximation for the length of an oval shape.
Mark a point in the center of the oval-shaped object.
Use the ruler to measure the distance from the center of the object to the "top" of the oval and the "side" of the oval. The larger of the two distances is called the semi-major axis, and the smaller of the two distances is called the semi-minor axis. As an example, assume the values for the semi-major and semi-minor axes are 5 cm and 3 cm, respectively.
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Square the values of the semi-major and semi-minor axes (i.e. multiply the numbers by themselves) and sum them together. In this example, 3 squared is 9 centimeters squared (cm^2) and 5 squared is 25 cm^2. Summing the two values together gives 34 cm^2. Call this result A.
Divide result A by 2 and take the square root of the resulting value. In our example, 34 cm^2 divided by 2 gives 17 cm^2, and the square root of this value is 4.1 cm. Call this number result B.
Multiply the result B by 2 and the constant pi (i.e. 3.14159...). In our example, multiplying 4.1 by 2, gives 8.2, and multiplying this number by pi gives 25.8 cm. This is the approximate length of the oval shape.
The more symmetric the oval-shaped object is, the more accurate the calculation will be.