Circumference =6.28318 r =3.14159 d
Diameter =0.31831 circumference
Area =3.14159r²

Diameter of circle of equal periphery as square = 1.27324 side of square

Side of square of equal periphery as circle = 0.78540 diameter of circle

Diameter of circle circumscribed about square = 1.41421 side of square

Side of square inscribed in circle = 0.70711 diameter of circle

Side of square of equal area = 0.8862 diameter of circle