Convert the area of a circle into an rectangle shaped area of the same size. Works much the same way as a circle to square conversion but you will have to enter the width of the rectangle in addition to the circle's diameter.
R = D ÷ 2where R = radius, D = diameter
A = π * D² ÷ 4where A = area, π = 3.14159..., D = diameter
C = 2 * π * D ÷ 2where C = circumference, π = 3.14159...., D = diameter
A = length * width
L = A ÷ Wwhere L= length, A = area, W = width
P = length * 2 + width * 2