If a circles radius is 20 inches what is the circumference?

1256 inches ++ Another Answer ++ The formula for finding the Circumference of a circle is C = Pi x D where D is Diameter and Pi is 3.1416. The Radius of a circle is one-half of the Diameter, hence the Diameter of a circle with a 20-inch Radius is 40 inches. Using the formula above, multiply 40 x 3.1416 to find the Circumference: 40 x 3.1416 = 125.664 inches.