Rectangle and Square
A rectangle is a parallelogram with four right angles.
The area of a rectangle is found by multiplying the length (L) by the width (W).
A circle is a closed curve of which every point on the edge of the curve is equidistant from a fixed point within the curve. The area of a circle is the radius squared (R2) multiplied by pi (~3.14). The radius is equal to one-half the diameter of the circle.
A triangle is a polygon with three sides. The area of a triangle is one-half the base (B) multiplied by the height (H).
An oval has an elliptical, or egg-like, shape. The area of an oval is the length (L) multiplied by the width (W), multiplied by 0.8.
To find the area of a large irregular shape, divide it into a series of smaller units equally spaced along a measured line. This method will calculate the area to within 5 percent.
- Determine the axis line. This is the longest axis of the shape, here shown as A to B.
- Mark several perpendicular lines along the A-B line. These lines divide the A-B line into several segments of equal depth. To ensure accuracy, use as many lines as possible. The more irregular the shape, the more lines you will need.
- Measure the width at each perpendicular line. In this example, there are 5 perpendicular lines: C, D, E, F and G.
- Calculate the area by adding the lengths of all the perpendicular lines and multiplying by the distance between the lines: (C+D+E+F+G) x Segment Depth.
The distance between points A and B is 60 feet
C = 19 feet
D = 22 feet
E = 23 feet
F = 19 feet
G = 13 feet
- Determine the axis line. Here A to B is 60 ft.
- Divide the axis line by a convenient number. In this example, the axis line is divided by 6 to make 10-foot segments.
- Measure the length of each perpendicular line. In this example, there are 5 perpendicular lines: C, D, E, F and G. Their measurements are listed above right.
- Calculate the area by adding the lengths of all the perpendicular lines and multiplying by the distance between the lines: (C+D+E+F+G) x Segment Depth
Area is: (19+22+23+19+13) x 10 = 960 sq. ft.