Circle Area & Perimeter Calculator You can change the size of the circle by using the slider. Press space to find the area and perimeter. The radius, area, and perimeter are shown in pixels. This project just finds the radius of the circle and uses the first 50 digits of pi to find the area and perimeter of the circle. It uses the formula πr² and 2πr. You can change the size of the circle by using the slider.
