For Squares or Rectangles: length (in feet) x width (in feet) = square feet
For example, a garden that measures 50 feet x 30 feet = 1500 sq. ft.
For Circles: 3.14 x radius (in feet) x radius = square feet
For example, a circular garden that is 20 feet across has a radius of 10 feet. 10 x 10 x 3.14 = 314 sq. ft.
(The mathematical formula for the area of a circle is Π · r2 - the Π symbol is pronounced Pi and represents approximately 3.142, and r2 stands for radius squared.)