First determine the radius of the circle from the area of the circle Use the radius determined above to calculate the circumference Area of a circle = np2 where r= radius n= pi = 3.14 100.608.7mm=mp2 to determine the radius, divide both sides of the equation by 3.14 32,040.98726mm = p2 Find the square root of 32,040.98726mm V32,040.98726mm r= 179mm Circumference of a circle = 2nr 2 × 179 × 3.14 = 1.124.12 mm