Measure the radius of the quadrant by measuring how far it is from the right angle to the curved edge.
Calculate the length of the curved side by the formula pi x r/2, where r is the radius. The circumference of a whole circle is 2 x pi x r. Because a quadrant is a quarter of a circle, divide the circumference of the whole circle by 4, resulting in (2 x pi x r) / 4 = pi x 4/2.
Add the length of the curved side to 2 x r, because each of the two straight sides of the quadrant is equal in length to the circle's radius.