The term "lineal footage" refers to the square footage of long, narrow objects. The proper term for this is "linear footage" because "lineal" refers to ancestry, but many people use the terms interchangeably. A board that measures 2 linear feet, for instance, is 2 feet long and one foot wide. Though circles never have a fixed width, you an calculate one's area to find the linear footage of a similarly sized 1-foot board.
Measure the circle's radius. For this example, consider a circle with a radius of 10 feet.
Square the radius: 10^2 = 100 square feet.
Multiply the result by pi, which equals approximately 3.142: 3.142 x 100 = 314.2. This answer is the circle's linear footage. A theoretical single board with a 1-foot width would need to be about 314 feet long to equal the circle in area.